I would like to update my expiry date on a new card but it won't let me

For Apple Pay, you cannot update the date directly. Its either updated automatically by your bank or issuer, or you need to remove the card and add it again.

See here: link-> Manage the cards that you use with Apple Pay - Apple Support

While you can't change your card number or expiration date, it should update automatically when you get a new card. If your issuer doesn't support updates, you might need to remove the card, then add it again.

so far you are not being helpful the software where are you put in the expiration date it’s messed up you must look at it to see I can’t fix it I’ve tried to put the card in several times but when you go to put it in the month for instants 08 there is a slash mark between zero and the year it will not allow you to put in 08 all it will take will be the zero because of the slash mark

I'm sorry, your post is a bit confusing.

Can you clarify your issue?

Normally, you should just need to enter the number 8 and then the year. You don't need to enter the trailing Zero in most cases.