I have seen some pet names with this ' in them but it says when I make a pet that that ' is not possible :( So why is it working for others but not me?

Lock Please :D

Symbols used to be allowed in pet names. But for some reasons, they changed the rule so now that you can't make pets with symbols in their names. Those pets you saw were probably created before the new rule was implemented.

There is a pet in the Adopt center with the symbol and it was made this month :)

Pet Name: J'adorais

I saw that pet in the pound a while back too and it had an older ID at the time! It confused me too but now that I think about it, I'm guessing someone adopted it, swapped the name with a newer pet, and then repounded it. Either way, certain characters aren't allowed when creating pets now, unfortunately. :(

That makes loads more sense now lol Thanks :D