Samsung Galaxy S5 — Triangle on top of phone

For weeks I have been trying to get rid of an annoying message that tells me I misdialed and quotes an email address (gmail.com) that I do not own. I have successfully dealt with it and removed the triangle.
It comes up on my desktop as a Google Play icon and claims that I did not sign in correctly. No amount of creating passwords will satisfy it.
The solution: Press on the Google icon and the app takes you to the app page. I saw that the show notification box was ticked and I unchecked it. Then restarted the phone and to my instant relief the triangle had disappeared.