Connecting to the app store

Hi everyone, i have an iPhone 7 ios 15.8

been having trouble for a long while connecting to the App Store.

i hadnt saved my username and password on my phone or at least it wasn’t in my saved passwords. So i was reluctant to sign out of Apple as a means of curing my app atroe issue.

in my laptop it is saved though.

so o decided to exit apple on my phone and then sign back in after. It wiped all my i cloud data in doing that as a result!

anyway , I signed back into apple on my phone no problem and hey prest I COULD now connect to the App Store! Yay !

but when I attempt to actually have anything off the App Store, it asks me to sign in.

i AM signed in ( surely?) but hey ho ill re sign in then , but when i do it wont recognise my apple username or password and it states this Apple id is not valid or supported , yet i signed back into apple with that same username and password!

so although now i can finally connect with the app store i cant use the app store?

what can i do?

any help is gratefully received.