Ok, it seemed to be fixed for me after a disabled wifi, and then went into settings on the phone and cleared trusted computers, then I said ok to trusting the computer again.

Same issue here.

FYI Apple, I have been searching all over the place for hours trying to figure this out. Wherever it is said that you can't preview macOS widgets, Google couldn't find it, and I couldn't either, nor is it mentioned in anything I could see in the WWDC videos about this topic.