My experiment doesn't initiate online

I try to run an online experiment in pavlovia but nothing happens there. It supposed that its a builder problem that I am using psychopy 2020.2.4. But I updated it recently. Please let me know if you can help me in that way

What sorts of error messages are you getting? And can you describe what you have tried?

Perhaps this resource will help:

Thanks for your response. It doesn’t show anything and I got this error
Traceback (most recent call last):
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\”, line 1240, in onPavloviaRun
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\”, line 719, in fileExport
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\scripts\”, line 73, in generateScript
compileScript(infile=exp, version=None, outfile=filename)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\scripts\”, line 242, in compileScript
_makeTarget(thisExp, outfile, targetOutput)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\scripts\”, line 214, in _makeTarget
script = thisExp.writeScript(outfile, target=targetOutput, modular=True)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\”, line 251, in writeScript
self_copy._currentRoutine.writeRoutineBeginCodeJS(script, modular)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 277, in writeRoutineBeginCodeJS
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 202, in writeRoutineStartCodeJS
self.writeParamUpdatesJS(buff, ‘set every repeat’)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 405, in writeParamUpdatesJS
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 399, in writeParamUpdates
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 435, in writeParamUpdate
valStr = str(val).strip()
TypeError: str returned non-string (type NoneType)

Also, the javascript doesn’t exist in html file