@Alain Tessier Thank you for reaching out to Microsoft Q&A. Apologize for the inconvenience caused on this. Could you please help us with more information Is your web app hosted on Azure App services or are you using Azure Virtual Machine to host your web app?
- If you have hosted your webapp on App service. I would suggest you run the
Webapp Down
Diagnostic report underAvailability and performance
in Diagnose and solve problem from portal to identify the issue whether there is an issue with application side or App service side.
Refer to this documentation to know about How to troubleshoot ASP.NET core and IIS core issues with ANCM failures.
Feel free to reach back to me if you have any further questions on this,