If your Recall Campaign is Active but no recalls are being sent, there’s usually a simple reason.
The most common are:
📅 There are no suitable appointment slots available
⏰ Today’s recall run hasn’t happened yet
👥 There are currently no eligible patients to invite
Work through the checks below to find out what’s happening.
1️⃣ Check you have available appointment slots
This is the most common reason an Active campaign stops sending.
Hippo takes your available appointment capacity into account before sending new invites. If there are no suitable slots available, the campaign remains Active, but no new recalls are sent.
How do I know if this has happened?
If you're a Super User, check the 🔔 bell icon in the top-right corner of Hippo.
You may see a No appointment slots available notification for the affected campaign.
The good news is that you don't need to restart anything. Once suitable appointments become available again, the campaign can automatically continue sending.
Which slots does Hippo count?
For a standard Recall Campaign, Hippo looks for available appointments that:
Match the slot type selected in the campaign
Are at a site enabled for online booking
Are within the next 21 days
Are at least 2 hours away
If Hippo can't find any suitable availability, the campaign won't send new invitations.
How do I get it sending again?
You can:
✅ Add more availability for the selected slot type within the next 21 days
or
✅ Edit the campaign and select a different appropriate slot type with availability
2️⃣ Check whether today's recall run has happened
Hippo sends recalls once each working day, from 11am.
Recalls aren't sent on weekends or bank holidays.
If you make a campaign Active or resume it after 11am, it will join the recall run on the next working day.
For example:
Tuesday at 2pm → first recalls from Wednesday
Friday at 3pm → first recalls from Monday
So if you've only just switched the campaign on and can still see 0 sent, it may simply be waiting for the next recall run.
3️⃣ Check the campaign is Active
Open Recall Campaigns and check the campaign status.
If it's paused, select Resume.
Remember, if you resume a campaign after 11am, it won't send until the next working day's recall run.
4️⃣ Check there are patients eligible to receive a recall
Having appointment availability doesn't necessarily mean Hippo has someone to invite.
A patient must meet all of the campaign's rules before they can be recalled.
Some common reasons your eligible patient list might be smaller than expected include:
🚫 Exclusions
If a patient is due an indicator you've added as an exclusion, they won't be recalled by that campaign.
If your campaign has several exclusions and nobody is being picked up, review whether they're narrowing the group more than intended.
🧩 Multiple target indicators
Depending on how your campaign is configured, combining indicators can make the eligible group more specific.
Check that your targets reflect the group of patients you actually want to recall.
🔍 Patient filters
Age, vulnerable group and birth month filters can all narrow the eligible patient group.
📨 Previous recalls
Some patients may already have received all of the messages in their Recall Flow, while others may be waiting until the minimum interval between recalls has passed.
💡 Not sure about a particular patient? Use the Patient Eligibility Checker in Recall Preview to see why they're included or excluded from the campaign.
See How Do I Choose Targets and Exclusions for a Campaign? for more information about patient selection.
5️⃣ Campaign sending, but fewer recalls than expected?
Your Maximum Recalls per Day is a maximum, rather than a target Hippo will always reach.
The actual number sent also depends on:
How many patients are eligible
How many suitable appointments are available
Your Invites per Available Slot setting
For example:
8 available slots + 1× Invites per Available Slot = up to 8 invitations
If your campaign allows 50 recalls per day but only has 8 suitable slots, Hippo won't send all 50.
If you'd like to invite more patients per available appointment, you can increase Invites per Available Slot.
💡 See Fill Clinics Faster with Flexible Recall Invites for more information.
🧑⚕️ What if patients have received a recall but can't book?
This is slightly different from a campaign not sending.
Appointment availability is live, so an appointment that was available when Hippo sent the recall may have been booked by someone else by the time the patient opens their link.
Here are some common reasons a patient might have trouble booking:
What the patient sees | What it usually means | What to do |
No appointments available | There are currently no suitable appointments available to them | Add more availability or offer to book the patient by phone |
Appointment no longer available | Someone else booked the appointment before they completed their booking | Ask them to choose another available time |
Booking link no longer active | The link has already been used to make a booking or has expired | Arrange the appointment another way |
Date of birth isn't accepted | The DOB entered doesn't match the patient's clinical record | Check the DOB recorded in EMIS/SystmOne |
💡 It's helpful to include your practice phone number in recall messages so patients know how to contact you if they can't find a suitable appointment.
💬 Still not sending?
If you've checked:
✅ The campaign is Active
✅ Today's recall run has happened
✅ Suitable appointments are available
✅ There are eligible patients
…and recalls still aren't being sent, get in touch with us.
Send us:
The campaign name
The date you expected recalls to send
There's no need to include any patient-identifiable information unless we specifically ask for it through an appropriate channel.
💡 If Hippo has temporarily paused recall sending for planned maintenance or another platform-wide reason, we'll display a banner in Hippo.
❓ Frequently Asked Questions
I switched my campaign on today. Why hasn't anything gone out?
If you made it Active before 11am on a working day, it can be included in that day's recall run.
If you made it Active after 11am, recalls will start from the next working day.
How far ahead does Hippo look for appointment slots?
Hippo looks for suitable appointments within the next 21 days.
If your next clinic is more than three weeks away, those appointments won't yet be counted as available capacity for the campaign.
EMIS/SystmOne shows free appointments, but Hippo says there aren't any. Why?
Check whether the appointments:
Use the same slot type selected in the campaign
Are within the next 21 days
Are at the correct site
Are available for Hippo to use
If everything looks correct but Hippo still can't see them, get in touch and we can take a look.
I've added a new slot type or clinician but can't select it in Hippo.
New information from your clinical system may not appear immediately.
Hippo syncs with EMIS/SystmOne every 24 hours, so newly created slot types and clinicians should become available following the next sync.
Who receives the "No appointment slots available" notification?
Super Users at the practice can receive these notifications.
Once appointment availability is restored across the affected campaigns, the notification will clear.
Patients are booking into the wrong type of appointment. What should I check?
Check the slot type and clinician selected in the campaign's booking settings.
Remember that booking links already sent to patients retain the booking configuration they were created with. Changing the campaign won't retrospectively change an existing patient's link.
🦛 In summary
If an Active campaign isn't sending, check these three things first:
📅 Do I have suitable appointment slots?
⏰ Has today's recall run happened?
👥 Are there eligible patients to invite?
In most cases, one of these explains why no new recalls have been sent.