Upgrade to iCloud+ does not work

I tried to buy more storage, so to upgrade to iCloud+, but it does not work, and it's not clear to me why. The error it gives to me again and again (after restarting my phone, checking the internet connection and payment method, etc.) 'There's a problem with upgrading your abonnement on iCloud+. Try again later'.

Could somebody please tell me things I could try to make it work?

The only things I can think of, is that the credit card I use for Apple Pay is on my husbands' name, not my name, or that the credit card is registered in Italy, while the phone setting is on 'The Netherlands'.

Thank you so much for your help.

Irene