You can contact the discord of the game or by email. Getting this, you probably play 931, and there you need to enter the patreon code before gaming it.
Viewing post in School Game / Sandbox, Simulator, RPG comments
I seem to have the same problem, so, does this mean I have to pay another $10 over on Patreon to play the game I bought here?
Edit: Don't mind me, I figured it out. I had to reinstall the game since it was locked in an eternal error before I could search for the code entering part.
Would have been nice if the game would have let me know, that it won't run without a code/email.