Can't remove doorbell cover

I had this doorbell for a long time. It’s the battery one with the one screw at the bottom. I’ve changed batteries on it a lot.
But… We’ve been unable to remove the cover to change battery for several days. The right side of the cover is just stuck as if it was glued to frame!
Thanks :smile:

Hi @user35162. In order to assist, we need to know which specific doorbell model you have. Thanks for this information.