activation lock apple id @gmail incorrect apple id need @icloud

Activation lock suddenly appeared in my iphone 6 plus. To restore I need to sign in with the associated apple id which is @gmail.com. When I put in the password I get the error incorrect apple id / password. I also tried my @icloud.com email but it won't let me use it, same error.

I log in to my icloud account in my computer and I can see the apple id is @icloud.com, and the primary email account to get notifications is the @gmail.com

I can be reached at both accounts according the apple id settings.

I tried to reset the password for the @gmail.com account as an apple id, I get an error that this email is not an apple id!!!

How can I unlock it if apparently the associated apple id "@gmail.com" is not even an apple id!!!

Thanks for your help.