Im quite new into scratch and was trying to make a game similar to a board game with multiplayer but when I went into fullscreen it didnt run the code, and i’ve tried using keybinds and other ways to start it.
If you want to see the code I published it (the name is grid moving tester) so you could try remixing it, but I still dont know if that will help.
Link for convenience
Snap! Build Your Own Blocks
In the Mover 1 Sprite, you should add a broadcast[player 1 turn V] under a when green flag clicked block to let player 1 move. Then when you click the Green Flag, you will be able to move!
Also, you can do

instead of

by clicking on the triangle on the if block.
I tried it and the else if tip was very helpful but it still doesnt let me move when i use the specific script, which is odd because it still runs all the other scripts in fullscreen mode.
I think the problem is that Snap only uses a ‘close enough’ number system and doing an equals comparison of numbers to screen positions will sometimes not work.
Are you seeing it work okay in the editor when the small project screen is display but it breaks when you go to full screen (again, in the editor?). It looks like some tiny position difference is occuring.
I added a round block to the position comparison and the black (gray?) circles show up in full screen mode. I also added some variables to show how the comparison is true in the smaller window but false when it goes to full screen for your initial state (when running in the editor).
If this helps with the issue that you are seeing then you could add round blocks to all of the other comparisons. However, what I usually see is that grid locations are calculated to be bigger than just one pixel by one pixel.