Score invalid notification

Several members have previously raised this problem, without apparent resolution. In the following screenshot most of my scores have been stored to the Musescore’s cloud (and display the cloud emblem), though I no longer rely on this. The 4 of the 17 scores in this shot that do not display the cloud emblem are saved to desktop and I can open them. All 13 with the cloud emblem involve my problem. If I click on any of them I get exactly the same report “Your score could not be opened. This score is invalid.” From receiving the notification I can only perform one function, namely click on the OK and it closes the notification. I cannot read anything else and cannot move the affected scores to the bin or otherwise delete them. Note several of the affected scores are titled “We Used to Know.” When the problem first arose with this score I tried again to save a workable version to the cloud, only replicating several versions of the same problem. Note that problem was over a year ago and I do not know why the scores are labelled 3 weeks ago. They are certainly much older than “Nowhere Man” which involves the same problem, but which is said to have been 6 months ago (sounds realistic).

It is probably of no relevance but my Musescore use is very basic. In the bass clef I write an electric bass guitar line; I usually add a simple repetitive drum rhythm and chords which tend mostly to use "acoustic grand piano” (playback sound quality being reasonable) from Svorzando.