Thank you for posting your query on Microsoft Q&A, from above description I could understand that you were facing issues while connecting to cloud apps using Global secure access client on end user device. Now as the issue got resolved you are looking for advisory on troubleshooting steps to follow in case issue reoccur.
Please do correct me if this is not the case by responding in comments section.
Apart from testing which you have described above, you may perform following checks:
- Try to switch the user i.e, login to the client with different user and see the behavior. Forces sign-in screen to change user or reauthenticate the existing user.
- Collect and validate the client logs from: C:\Program Files\Global Secure Access Client\Logs
- Validate the event logs from Applications and Services/Microsoft/Windows/Global Secure Access Client/Operational
- Ensure that IPv6 is disabled.
- DNS over HTTPS (Secure DNS) needs to be disabled.
- Block QUIC when tunneling Exchange Online traffic Kindly refer to the link: https://learn.microsoft.com/en-us/entra/global-secure-access/how-to-install-windows-client#troubleshooting for reference.
Apart from steps above you may also validate Global Secure Access (preview) traffic logs
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Thanks,
Akshay Kaushik