Why isn't my Power Automate Bookings trigger firing?

Check these in order#

1. Your role on the booking calendar#

Microsoft's connector reference says: "Only Bookings admins can create flows using Appointment triggers", and that this is "different from tenant admins". Team Member, Scheduler, Viewer and Guest roles can't create them. Open the calendar in Bookings, go to Staff, and confirm your account is listed with the Administrator role. Errors such as "Staff not part of Bookings Business", "Invalid authority" or HTTP 403 when saving the flow point here. The roles are compared in what each Bookings staff role can do.

2. The booking page SMTP address#

Each trigger has a Booking page field. The dropdown only lists calendars you've opened recently and are an admin of. If yours is missing:

• Open that calendar once in the Bookings web app, then reload the flow designer.
• Or choose Enter custom value and paste the calendar's SMTP address. Microsoft's FAQ says it's shown under Integrations → Power Automate on your Bookings page. It's also the address in your public booking page URL after /book/.

3. The five-flow limit#

Microsoft documents a hard limit: "Only 5 flows can be created per Bookings Mailbox", counted across every admin. Going over returns HTTP 429. Old test flows count too, and Microsoft notes that errors during flow creation aren't always shown in the portal, so a flow can look saved without its trigger being registered. Delete unused Bookings flows, then turn the flow you need off and on again, or recreate it. If you need several outcomes from one event, add more actions to one flow.

4. SMTP on the booking mailbox#

In a December 2025 Microsoft Q&A thread, a flow that never triggered and showed no run history started working after the poster enabled SMTP on the mailbox: "We had this off, but it looks like it is necessary for the trigger to work." Microsoft doesn't document this requirement, and the thread doesn't say exactly which SMTP setting was changed, so ask your Exchange admin whether SMTP has been disabled for the booking mailbox or tenant-wide.

5. Conditional Access and app consent#

The same thread showed invalid_grant / AADSTS50013 errors from the connector in a tenant using Conditional Access and app-consent policies. The suggested steps were to allow the Bookings connector in your app-consent policy, make sure the account creating the flow meets your Conditional Access requirements, then delete and re-create the Bookings connection to get a fresh token.

6. Licence and cloud#

The connector needs a Bookings licence, and it isn't available in GCC, GCC High, DoD or 21Vianet.

Testing without false alarms#

"Flow run timed out because the starting action was not performed" usually means you clicked Test and no qualifying booking arrived while the test was waiting. Start the test, then immediately make a real booking on the public booking page for that calendar. A booking on a different calendar, or a "Bookings with me" page, won't trigger it.

When only the Updated trigger fails#

Two Microsoft Q&A threads (2024 and 2025) describe When an appointment is Updated showing zero runs after appointments were edited, while Created kept working. Neither got a fix. What Microsoft does document:

• Update events don't tell you what changed.
• In group bookings, the second and later attendees fire Updated, not Created. If you rely on Created to capture every class attendee, you'll miss people.
• Cancel Reason isn't populated for one-to-one bookings.

If you need reliable change detection, the poster in the 2025 thread fell back to polling Microsoft Graph: read a rolling date range from calendarView and compare each run with the last. The pattern is outlined in Bookings webhooks and alternatives. For a full Created-trigger flow into a CRM, see the Power Automate CRM guide.

Other errors you may see#