There is a trick for that, if you open the console, you will see:
Discourse v3.5.0.beta2-dev — Commits · discourse/discourse · GitHub — Ember v5.12.0 - so this is from March 4, quite old.
Additionally there is an error there in the console they need to handle which mentions credentials this very much could be related.
Given site is quite old, moving this to support can you double check if you can repro this here on meta?