As I already said, I have tried different browser, incognito mode, even different PCs. I even installed a new portable browser. Tried a mobile browser, with and without wifi. All have the same problem. Maybe you are geoblocking some requests for German users?
I can sign in to Atlassian without a problem. I have other cloud based Jira websites that work without a problem. It’s only the Hibernate Jira that causes problems. I’m out of clues.
The error even shows up without signing in. Just opening the Hibernate Jira is enough for the error message to show up.
Maybe it’s still this issue: Trying to report a bug in Hibernate