Following Java instructions, but Sentry does not receive any events

By following Zentry’s instructions for Java at

Everything seems to be working on client side. All API calls are successful. But on Sentry side no events or issues are received at all.
Where should I look at? Any hints how to diagnose?
Thanks in advance!

If you can, try tracing the requests made on the client side to see if your app is actually sending stuff to your Sentry server. You can also test your server with the CLI to see if it can receive events: https://docs.sentry.io/cli/send-event/

My app runs on Google App Engine. That might be the issue.
I could make it work on standalone Java applications, but not from App Engine. Following Sentry’s instruction, I use this library:

io.sentry
sentry-appengine
1.7.23

Did anyone make Sentry work on App Engine?

Thanks!

I’m not familiar with App Engine and Java deployments but our docs seem to have some things for this: https://docs.sentry.io/clients/java/integrations/#google-app-engine

Have you followed any of this?

Yes, that is what I followed.

It wasn’t clear from your other responses so I have to ask again. Have you tried the following:

This is to verify that your Sentry server is reachable and accepting events properly. Or is this an existing Sentry instance that already have other projects?

Yes, the server does accept events properly. Standalone Java application can send events to the server as well.

Then I really don’t know what the issue is. Maybe Google App Engine needs a setting to allow requests to your Sentry server? Or your server is not accepting events from GAE due to firewall/IP restrictions?