cant boost post error

I can't add a payment method to boost posts on instagram everytime i try i get multiple errors that flash quickly and then it settles on "there was a problem adding your card" after i click 'add new payment method, has anyone experienced the same or have a fix?

I'm in talks with facebook/Ig support but they are slow and so far they have only redirected me to add money via facebook business, which does work for the FB page but not for IG page.

-problem is on multiple accounts
-ive tried multiple different devices
-same problem everytime.

anybody have experience in fixing this? Thanks!