Hey there all,
I'm in the same boat as the OP and with so many other people on this thread that followed. The "Your Phone" app used to work as advertised until a recent update to it from the Windows Store was installed. Since then the app has refused to get past 60% progress (although I do get confirmation emails from Microsoft stating that my account has logged in from a new device) in the desktop app. I have tried a completely fresh install from both the Microsoft Store and from the Google Play Store, and have installed the Android phone app on a Samsung Galaxy S9 and on a Google Pixel 4a 5G. With each phone the Windows 10 app comes to a screeching halt at exactly the same point in the installation process, and inspecting the task manager shows that the Your Phone app is at 0% CPU activity, 0% disk activity and 0% network activity.
At the moment, after its recent "update", the Your Phone app is a useless lump that is sorely outclassed and outperformed by pretty much everything else out there that does a similar job - regardless of how inefficiently any competitor's offering may be right now. It least those competitors are doing something, no matter how badly...