Forum: cannot log in from some browsers " there was an error authorizing your account"

I try to log in this forum using my MojeID account. With Google Chrome, it works, with Firefox, I get "Sorry, there was an error authorizing your account. Perhaps you did not approve authorization? "

In both cases, I can see and edit my MojeID profile so I assume MojeID works and there is a problem between MojeID and this forum (but I don’t see why it is browser-specific).

I have got the same issue

Ubuntu 18.04.1 LTS and browsers:
Firefox 64.0 (64-bit)
Google Chrome: Version 71.0.3578.80 (Official Build) (64-bit)

Works for me in both cases.