Troubleshooting game display issues can be a process of elimination. Patience and persistence are key. Hopefully, one of these steps will help you resolve the "Serious Sam 3 cannot set display mode" issue and get back to enjoying the game.
This is advanced but effective:
The "Fatal Error: Cannot set display mode" in Serious Sam 3: BFE serious sam 3 cannot set display mode
Find and change these lines to match your monitor (e.g., for 1920x1080): gfx_pixResWidth = 1920; gfx_pixResHeight = 1080; gfx_bFullScreen = 0; Troubleshooting game display issues can be a process
If you are trying to launch Serious Sam 3: BFE only to be greeted by a black screen or a crash with the error you are not alone. This is a common issue with the Serious Engine 3.5 when it fails to handshake with your monitor's resolution or refresh rate. This is advanced but effective: The "Fatal Error:
C:\Program Files (x86)\Steam\userdata\[YourUserID]\41070\local\ SeriousSam3.ini : Open this file with Notepad. Adjust Resolution