I just recently installed 10.15 Beta (19A546d) and am not able to drag and drop files into an app with shared files via Finder->iPhone->Files->appName. I can see the icon change to a PLUS sign but there's no visible indicator that the file is transferring. Even after waiting some time, I don't see the file transferred. I see 10.15 beta 8 is available so am installing that right now to see if it's fixed. Otherwise, how were you able to successfully a file back in Beta 2?
Sorry for the delay: I didn't get notified of your comment
I've had a couple more occasions of files not transferring, each time because (I think) the iOS 13 and Mac OS 10.15 betas were not compatible, i.e. I had not installed one or the other of the latest betas.
All is well at the moment with the latest betas.