
There are a few more threads to this problem. See:
here: https://app.roll20.net/forum/post/10916320/error-finishcurrentpolygon-upon-opening-games
Sorry you’re having trouble—this error appears when WebGL is not enabled in your browser. Dynamic lighting uses WebGL, a Javascript API for rendering high-performance interactive 3D and 2D graphics without the use of plug-ins. WebGL is available on most computer systems and is supported by Google Chrome and Mozilla Firefox, the browsers for which Roll20 is optimized.
On Chrome and Firefox you’ll need to turn on Hardware Acceleration in your advanced settings. You can test whether WebGL works using this link. (Also posting this to the other threads!)
It seems it was an error with my graphic card crashing, I reseed the PC and now it's working properly.
I am posting this to combine these into one mega-thread:
https://app.roll20.net/forum/post/10916320/error-finishcurrentpolygon-upon-opening-games/
For those still having issues please post in the other thread.