Please check the "Long Game" achievement fix.
If the game is paused, the counter also stops counting, as the whole game stops.
There is some inexplicable problem with it.
FIX GIVE ACHIEVEMENT "LONG GAME"
Source: Steam Community (opens in a new tab)
Build and release context
Steam update times within 24 hours of this post. Matching dates do not confirm which build it describes.
Build 17562100 · public branch
Steam updated · First observed