Hey, @nick-parry thank you for your feedback.
(1) "Sometimes it just starts loading and then goes black." This is something we experience quite often, when this application runs on NVidia cards. We use features of DirectX9, that NVidia does not fully support in all of their drivers. On most NVidia cards we tested this on, there is some kind of graphics error. This reaches from a completely black screen to just broken transparency. On every AMD card we tested on everything works just fine.
(2) "Other times it says no GPU" Yep, just try to start it again. Sometimes the d3d device initialization times out and the next time you start it it just works fine. We know about this issue, but did not find a way to fix this yet. Sorry.
(3) "Another time it gave me this https://pastebin.com/WXTsv0WK" I assume you got this one after trying to execute it multiple times. It means another instance of the program is still running. End all instances of this program and run it only once at a time.
(4) "Im using Windows 10 with i7-4770k cpu and a 2070" As said in (1) NVidia does not fully support all features of DirectX9. In our case it's most likely the problem that they do not support multiple depth buffers which are crucial for our transparency rendering technique. In our last LudumDare ([LD44][lnkLD44]) we used OpenGL instead, but experienced quite similar problems.
But hey, at least now we can add the "GeForce RTX 2070" to the list of not working cards...
[lnkLD44]: https://ldjam.com/events/ludum-dare/44/boredom-be-gone