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Error connecting to Bookings

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Posted on by DH-30101721-0

I get the following error, wehn I try to connect PowerAutomate with Bookings

Fehler bei der Anforderung für dynamische Aufrufe: "Failed to get onbehalfof access token: connectionId=microsoftbookings, message={\"error\":\"invalid_grant\",\"error_description\":\"AADSTS50013: Assertion failed signature validation. [Reason - Key was found, but use of the key to verify the signature failed., Thumbprint of key used by client: 'C8453099758BD74EC273EED06765926DE39BDEC4', Found key 'Start=10/01/2025 05:16:36, End=10/01/2030 05:16:36', Please visit the Azure Portal, Graph Explorer or directly use MS Graph to see configured keys for app Id '00000000-0000-0000-0000-000000000000'. Review the documentation at https://docs.microsoft.com/en-us/graph/deployments to determine the corresponding service endpoint and https://docs.microsoft.com/en-us/graph/api/application-get?view=graph-rest-1.0&tabs=http to build a query request URL, such as 'https://graph.microsoft.com/beta/applications/00000000-0000-0000-0000-000000000000']. Trace ID: cc4d5c4a-fdcb-4986-a39b-1fbfe0a24a00 Correlation ID: 01e3101d-cb03-4832-908b-ed0a78de1b94 Timestamp: 2025-10-30 16:59:01Z\",\"error_codes\":[50013],\"timestamp\":\"2025-10-30 16:59:01Z\",\"trace_id\":\"cc4d5c4a-fdcb-4986-a39b-1fbfe0a24a00\",\"correlation_id\":\"01e3101d-cb03-4832-908b-ed0a78de1b94\",\"error_uri\":\"https://login.windows.net/error?code=50013\"}".

I checked the Entry App-Registration, but there is no App registered regarding Bookings. Do I have to set this up manually or is there an automated way?

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Expiscornovus 33,874 Most Valuable Professional on at

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Hi @DH-30101721-0,

Are you using the standard Bookings connector? If that is the case, normally you just need to create a connection with your bookings mailbox and having the right permission on that bookings page/mailbox.

Afaik you don't need to create your own app registration, unless you want to use the Graph API and the HTTP connector.

Please double check if you have the right permissions and see if you are hitting any of these limitations:

https://learn.microsoft.com/en-us/connectors/microsoftbookings/#known-issues-and-limitations

Happy to help out 😁

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TC-24031051-0 2 on at

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I'm having the same problem. Did you find a way to resolve this?

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deepakmehta13a 322 on at

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Hi,

This error (AADSTS50013 – invalid_grant / signature validation failed) usually indicates an issue with the authentication token or cached credentials rather than something you need to manually configure.

For the Microsoft Bookings connector, you don’t need to create an App Registration manually, it’s managed by Microsoft. Try removing the existing Bookings connection in Power Automate and re-creating it, and also sign out/in to refresh your credentials.

If it still persists, check with your admin whether conditional access policies or expired keys are blocking the connection.

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