Well, this clearly an issue that many people are experiencing. Apple Support's troubleshooting/repair instructions don't work for every person who I have seen that is having the same problem. The "best" answer I have seen has to do with a lack of "end to end encryption" - see below. These things really do have a negative impact on user productivity - once enabled and now not. Bummer.
See Marcy Matties...Sep 22, 2019 3:47 PM in response to amyb32
I had also gone through all of those steps. In my other Googling I saw a thread from a couple of months ago between some of the beta testers. Their guess is that it has to do with "end to end encryption" - which I don't understand, but it doesn't matter. They seem to think that it won't work until Catalina comes out. Something about end to end will work once there is the combination of Safari 13, iOS 13, and Catalina. It is really a disappointment for me because I travel quite a bit and frequently need tabs from my laptop when I'm gone. Or when I'm home need some tabs I found/used when I was gone. If anyone else finds a solution before Catalina I would be very grateful!