This usually means that a background save has not completed.
When the save button is greyed out, you should also see the background tasks icon (circled) at the bottom right of the screen:
Click on that and it should display the progress of the file being saved and, possibly, errors that happened while saving it.
Any clues there?
If there are no clues and it is happening often, you can turn off the background saves at tools > options > global
Thank you. I'll look out for the notification on the bottom bar and let you know what happens when the issue is replicated next.
I've tweaked a couple of the save settings too, to see if that helps.
Thank you so much.To turn off the autosave worked, but this must be a bug or something. I have x7.