Changing Email Address in MyAccount?

Hello Allan,

We have replied to your other post: https://support.avg.com/answers?id=9060N000000g99X .
Keep up the conversation on single thread to get quick assistance.
Thanks.

I just tried changing my address TWICE in "MyAccount".  The FIRST TIME using an older laptop running WindowsXP and using FireFox as the browser.  The SECOND TIME using a new-ish HP laptop running Windows10 and using MS EDGE as the browser.  
 
During BOTH ATTEMPTS, I received an error response saying the new address was already [in the system].  HOWEVER, I cannot figure out how to switch to it.  HELP!!!

Hello Allan,

We have replied to your other post: https://support.avg.com/answers?id=9060N000000g99X .
Keep up the conversation on single thread to get quick assistance.
Thanks.