Run a Steam Verify operation against the game, see if that finds anything to fix.
If not Please attach here the game log C:\Users\<UserName>\AppData\Local\Introversion\Prison Architect\debug.txt
To see the AppData folder you'll need to enable View Hidden Items in File Explorer.
AND DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.
THEN try Safe mode - does that work?