Any reason why I would be unable to edit the screen?
I right click and it seems to be disabled? Cant edit it at all 
Is it set to custom or layout on entity screen settings in back end?
Only Admin can enter Design Mode.
Sometimes I have sen it get “stuck” when switching users, and I needed to logout, shutdown, restart SambaPOS.
That may be he problem. I’ve left now but I’ll do it remotely tomorrow night now.