Opening a issue redirects to login page

[Andis59]

When I try to open an issue I've created in a project, it redirects me to the login page, even though I'm logged in as the user that has created the Project and the Issue.

If I then login (again) I will end up at the same login page...

Why and how do I fix this?

Using bugnet 1.6.339 IIS 10.0.17134.1 Windows 10 Pro

There is an old question but it's closed and no solution. #145