I was having the same problem so after reading this thread, I went into Users/myname/Appdata/Affinity/Photo and was interested that the date on the 1.0 folder was 9/11/ 2018. I renamed the folder to 1.1 and copied it elsewhere. I didn't bother holding down the ctrl while booting up, but I saw it created a new 1.0 anyway.
The 1.1 folder shows that many of the files have last year's dates so this is obviously a potential pointer to the core issue.
Now I have proper processing back and I can stop using RawTherapee which I had to fall back to. I had seen lots of other suggestions for sorfting this bug out and wasted ages trying every permutation. If it helps, I have zipped the 1.1 and attached it
1.1.zip
Delighted that while adding a custom keyboard shortcut via preferences, you get an immediate warning triangle of any conflict and that your key combo shows up in the toolbar immediately. However the Help programme does not pick that up so it would be good to have a method of printing out the current list of shortcuts. That is a strategy that could help a lot of software.