Same for me
@OrsonKartt
During the first Covid lockdowns I went from lifting weights most days to sitting all the time, and developed a frozen shoulder during this period. I suspect the inactivity was a factor.
I had a cortisone/hydrodilatation injection which significantly reduced the symptoms for a couple of months, though it near doubled my insulin requirements for a while, and the relief was temporary.
What really fixed it was getting back in the gym, and doing lots of dead hangs (gripping a pull up bar and supporting your weight off the ground with straight arms. Most gyms also have assisted pull up machines for if you can't hold your full weight). At first I could just manage overhand grip, then neutral and eventually underhand.
In the earlier stages stretching after hot showers helped too.
Now I'm back to pull ups, chin ups, overhead pressing, even overhead squats without any problems or pain. My internal rotation on the affected shoulder is still a few degrees less, but I continue to work on it.