Musescore (version 3.3.4.0) Windows 10

Help !
My Musescore has stopped working. It has been working as normal, but as I was going through my folder of scores playing back each one in order to clear out out-dated or surplus ones, after listening OK to about 50 scores further scores would not load. I investigated and found that the Musescore app itself would not load.
This is a serious problem for me as I have new partly-written scores to finish.

I should be very grateful for any suggestions to get it back working.