I have two Ticwatch E watches. One is connected to an iPhone 7, one to an iPhone 6. The one connected to the 7 will generate a QR code, although it didn’t at first. I gave up on the problem for a couple days and when I came back, it worked. The watch connected to the iPhone 6 gets the service unavailable error. Like the others, this is the only app I am having a problem with. You should find another way to sync devices, because I have read a lot of threads about this across the net, and a lot of people are having this problem.