In case this is of use to others in the future:
Event Log didn’t show anything.
Scrivener was opening once I got the programme into compatability mode for windows 7, but would shut down instantly as soon as I tried to open my project.
I had it set up to open on the current project automatically on load originally and I suspect that was what was stopping it from loading. I think the problem must lie with the actual file/project. Somehow via the change to windows 7 compatibility mode scrivener stopped loading with the project open, which allowed the programme to actually launch. But as soon as I went to open the project it crashed. Thus my theorey is that there was a problem with the project file.
I should add that the backup versions of my project were all missing huge sections and very strange in composition.
As mentioned already, I didn’t have multiple versions open, I was shutting them down via task manager or via reboot.
It wasn’t an issue with it running off screen either.
Support eventually got back. This was their suggestion (it didn’t work for me, but maybe it will for someone else):
"Reboot the computer using “Safe Mode with Networking.” Here are the instructions:
Make sure you use “Safe Mode with Networking” and not the normal Safe Mode. Once you get booted up into Safe Mode with Networking, launch Scrivener. Presumably it will open. Let it sit for a couple of minutes, then reboot your computer into regular mode and try launching Scrivener again.
Scrivener periodically dials out to the activation servers to let them know that the current installation is still active (this allows us to free up activations that go completely dormant, such as when a hard drive crashes so you have no opportunity to de-activate the software). Normally, if this fails for any reason, Scrivener should just ignore it and start up anyway.
However, I’ve seen cases recently where something on the system blocked Scrivener from doing this task in such a way that instead of “failing gracefully” like it is supposed to, it just hangs. If the reboot into Safe Mode works, that means this theory is correct. It will also give Scrivener an opportunity to complete the function, after which it won’t try again for a very long time."
As I say, this did nothing for me. Opening it in safe mode with networking made no difference to what happened during safe mode use or upon reboot.