Why do I keep getting an error message that says couldn't sign in?

[AC Question]

It keeps on saying "couldn't sign in"

I have a new e-mail address. But am unable to change it to my new e-mail address.
The username is on my old address.
The server refuses to accept the new e-mail address.

 

[anon8380037]

Re: It keeps on saying "couldn't sign in"

Hello.
There is some information missing.
Did you make another Gmail address and want to switch your device to this.
What username did you want to change.