I have used TeamViewer, on and off, for many years, and it has always worked great.
But now, it never works. And gives a totally useless error message, both for me and the partner computer. I attach it.
Our computers and Net connections are always fine, nothing else wrong here. Yes, we both have the latest version.
I am thinking of subscribing, after years of modest, free use -- but I certainly won't do that, unless it starts to work flawlessly again . . . .