"Go to first unread" not working...

... on old threads.

This thread popped up on the recently posted radar:

https://photography-on-the.net …/showthread.php​?t=1007816

It is four years old. Even tho I have posts in the thread, there was no "Go to first unread" option.

Does the option not appear on old threads - those started before the new forum app was installed?

It doesn't apply on pre-AMASS threads because that information didn't carry over, but you'll (or you may) also notice that it doesn't appear on older post-AMASS threads here; the software only tracks the last 1000 or so threads you've read, IIRC. Anything beyond that will show as "Unread".