What if the boss says to have fun on the job but they get upset when you do?

He means that you should spread corporate cheer aka “case of the Mondays” “livin the dream” banter with coworkers while you strictly adhere to your scheduled work time

Maybe your boss needs to be more specific when saying have fun.

He has no clue what's going on most of the time

He might be gathering evidence to fire you

tell them to have fun

Gaslighting

He means keep your privates off the printer lol