Unable to subscribe to Fitness app

I am trying to redeem a code I got from O2. Which works, but when I go to confirm that I will be billed from the 9th of April 2023. I get the following appear.

I click ok and nothing happens.

I went to Settings>Apple ID>Payment

where it asks me to update my card details via the security number on the back of the card. Which I did. But I was still unable to subscribe to the app. I went back to the payment section on my Apple ID it asked me to again update my card. Which I do. I go back to the app and I was again unable to subscribe to the app.

I go back to the payment section of the settings, again I input the information to update my card. Instead of trying to subscribe to the fitness app. I go to the iTunes Store and I was able to purchase The Princess Bride.

I went back to the fitness app and again I am unable to subscribe to the app.

Can someone please help.