I don’t know how to fix your problem but I am curious about it.
I assume you have an old iPhone tied to your iCloud account. What happens if you untie that phone and wait like a day (some iCloud stuff is weird and can take about 24 hours to update server side info)
In order to update my Apple TV, they tell me I have to have a newer phone.
Similar to: https://www.reddit.com/r/appletv/comments/ys4z35/apple_tv_is_now_unusable_without_an_iphone/
Now you can use it, but guess what is required for future app updates? Later OS updates. It’s a trap.
I don’t know how to fix your problem but I am curious about it.
I assume you have an old iPhone tied to your iCloud account. What happens if you untie that phone and wait like a day (some iCloud stuff is weird and can take about 24 hours to update server side info)