Thank you for the detailed report! It's so nice: reproduction steps, actual behavior, expected behavior, the relevant log and settings files, what you tried so far. :sogood: Please teach everyone else how to report issues! :grinteeth:
A few other users have reported similar behavior, though usually reported that Spine runs once then they need to reinstall (which resets prefs.json) to run again. Unfortunately we have not been able to reproduce the issue.
Nothing stands out as being problematic in your prefs.json file. The one thing that may be related is:
"monitor":1,
Can you please try deleting this value? This is the monitor index for the monitor Spine was on when the file was saved. It is used to open Spine on the same monitor. It may be that something about doing that fails and the Spine windows isn't created successfully. When the Spine window is shown, it hides the launcher window, so it seems the failure prevents Spine from getting that far. It is very odd that the failure is silent.
If deleting the value allows Spine to run, you can change the value to:
"monitor":-2,
This will prevent Spine from trying to reopen the Spine window on a particular monitor. Instead it will always open on the primary monitor.
Before setting to -2 though, it would be helpful if we can find some more information about the problem. If you delete the prefs.json file, run Spine, then close it without it being maximized of full screen, does it run the second time? My thinking is maybe the maximized, non-maximized, or full screen state of the window is relevant, as when Spine runs it tries to create the window in the same state it had when closed.
I wonder what could be different about your multiple monitor setup that causes the problem, as we don't see it on ours. What graphics card are you using? Do you have the latest drivers? Can you think of anything that could be unique about your setup?
BTW, I see you are running 3.8.72. The last few 3.8 releases have some important fixes for stability. We've just released 3.8.97.
