Local Host didn't send any data; NoneType Object has no attribute in 'MainLoop'

When trying to run the experiment in local debug mode, I receive the error “Local Host didn’t send any data. ERR_EMPTY_RESPONSE”.

When exiting PsychoPy, I receive the error "NoneType Object has no attribute in ‘MainLoop’ (screenshot below).

I’m receiving these errors also on experiments that had previously been working successfully with no issues.
Any help on this would be greatly appreciated, thanks!