Answer

If you bookmark the main Hub login page, it will result in a URL like the following:

https://localhost:8080/?state=16%2Fb...0-3db0c583892f

When you go to access that page, you will likely find that you are presented with a 400 error, rather than the log-in screen. This is because the URL that gets bookmarked contains a one-time browser session ID. After the session expires, that URL is no longer valid.

In order to resolve this issue, bookmark the root of the server (i.e., https://localhost:8080) instead.