I’m no script expert by any means, I’m afraid.
If Jitai uses WK Open Framework, make sure that WKOF is in the number 1 spot on your TamperMonkey dashboard.
The only other problem I can readily think of if you followed all the install instructions is this mention in the Jitai thread: Whoops, wasn’t paying attention for a moment.
Did you download fonts for the script to use in randomization?
If it’s none of that, I would have no idea, and I think you’d be best off commenting in the Jitai thread and getting help from the script developer. ^^
Good luck getting to going!