Soo.. It's been a while since this problem started and I still get a blank screen when trying to log a cache or travel bug. The link provided by ColleIsarco also does result in a blank page.
On mobile works, but is just not as comfy.
Win 10, 64bit, latest, Firefox 121 with various extensions - no log possible
Firefox 124, brand new, not modded at all, on a completely fresh win 10 - no log possible
Chrome 120 - no log possible
Edge (Yes, I tried it) - no log possible
Interestingly enough I just found out that only clicking on the 'log geocache' button in the listing does result in a blank page. Opening the logging page via a draft works fine.
Clicking on a 'log geocache' button gives an URL like this: https://www.geocaching.com/seek/log.aspx?ID=7487274&lcn=1, which results blank
Clicking on a draft gives an URL like this: https://www.geocaching.com/live/geocache/GC8H3XX/draft/LDA5433K/compose, which works
I'm no hardcore tech guy, but I'd say, as logging is still possible via drafts, there is something wrong with the generated link applied to the log/discover button.
Soo.. Hello Groundspeak, it's at least three months! Does anyone at HQ care?