Workouts stop registering as being completed

I have noticed that none of the workouts I have completed recently are recorded as completed - that today’s date is not added. I initially thought that the bug was due to the fact that I had previously completed a work out and it wasn’t ‘over writing’ the date with a more recent one. I have repeatedly done the 10-12 week ftp builder. But today it refused to save a completely new and completed workout for one I’ve never done. The data uploads to strava fine. I’m just running this on a standard PC. Any ideas?