As I said I've already successfully done this on several other PCs and browsers (Firefox and Chrome). I'm trying to do this on my tablet with Edge - neither Chrome nor Firefox are very finger friendly. Your comment about it just starting recently leads me to believe that this is another case of Google jabbing at Microsoft. I really wish this would stop.
Got the same thing on my SP3 using Edge. I much prefer an app on my computer that is stable, rather than relying on "pairing" ... so I've gone back to Verizon Messages+, which works VERY well on phone AND computer.
I am also getting the error using Chrome as the browser, issue is not limited to Edge. In addition to Chrome, I also tried Firefox and had the same issue. I also tried using a Chrome Incognito window and got the same error