Change of email to my Apple ID

Hello, i have linked by Apple ID to my corporate email address. i have icloud photos as well as Apple TV subscription tied to it. This was never as issue till last week where we have been notified to discontinue using our corporate email addresses as our Personal Apple ID's. I have searched online for all the instructions of moving out from my corporate email address to a new personal email address - but each time i try and update my email address - Apple gives an error "Could not update email - You cannot set up an Apple account using this email address. Please try again using a different email address".

I have created a NEW icloud email as well as a new gmail address - and these are new - so there is no way its linked to any account anywhere - still my appleid will not change.

All i have been to achive is that both my new Icloud and gmail addresses are added to profile. So i have my Primary email and then 2 new emails listed - however i cannot change my Primary.

What am i doing wrong and how can i achieve

1 - Change the Primary email from Old to New email addresses

2 - update icloud photos and Apple tv to show my new primary email address and not my old corporate email address.

thanks in advance for your help and guidance.