"The score cannot be uploaded, as we don't support this version of mscz files yet."

This message is appearing when I try to upload a file (see attached). https://musescore.com/user/1236216/scores/6320339
The file takes a while to upload (not surprising given the file size) and then says it has been processed 100%. I clicked "next" to bring up the page where the score is actually displayed and there is no score, just an error message that reads:
"The score cannot be uploaded, as we don't support this version of mscz files yet. Sorry for the inconvenience."

My version of Musescore is 3.5.0.13199, Revision 43c5553 and I am apparently fully up to date.

It's baffling me because it uploaded alright the first time. I realised I had missed a couple of notes here and there and also altered the reverb settings a bit, so I revised the score and tried to update the score on top of the previous one.
Then the above error message came up.

Is there any way of getting this to upload properly? Any help would be much appreciated.

Kind regards,
Dave.