Can't link template: "Browser or app may not be secure"

I haven’t used this in over a year. Microsoft Excel opens up a new template, but I can’t get the Tiller add-in to log in. I get this error message: "Could not log you in. Browser or app may not be secure. "
You can go back, but you just repeat the process. There is no alternative.

Any ideas?
thanks,
John

Your answer is here: