Having the same issue...
In C:\Program Files (x86)\Origin Games\The Sims 4\Game\Bin\Default.ini the keys are defined.
line 21:
[GameplayKeys]
tilde = |clock.toggle_pause_unpause
grave = |clock.toggle_pause_unpause
zero = |clock.toggle_pause_unpause
one = |clock.setspeed one
two = |clock.setspeed two
three = |clock.setspeed three
four = |clock.toggle_pause_unpause
I added the grave to check if that might work, since that is the name for the ` symbol. Unfortunately that does not work.
So I added the line 'four = |clock.toggle_pause_unpause' (as shown above in bol), and this works. I can now pause the game with the 4 key.
You can also shift all keys 1 to the right, so the 1 key pauses the game, 2 for speed 1 and so on.
Too bad this isn't really a fix, but just a workaround... At least this is better then using the P key :D. Hope it helps.
