Contact Gmail by phone, if you can't add your email id on the Gmail app.

Gmail is one of the important application to send and receive an email. And its app make it easier to use by adding your id. If you are not able to add your email id in the Gmail app, then you should confirm you enter the correct user's credentials like id and password and also check your internet connectivity. If you still can't do it, then you should  contact Gmail by phone  or contact us to resolve this issue.