Cant upload experiment online - 'NoneType' object has no attribute 'project'

Description of the problem:
hi, whenever I try to upload my experiment to the pavlovia, i get the following error:

Traceback (most recent call last):
File “C:\Program Files\PsychoPy\lib\site-packages\psychopy\app\pavlovia_ui\”, line 166, in submitChanges
self.parent.project = self.project
AttributeError: ‘NoneType’ object has no attribute ‘project’

the original version of the experiment was built under psychopy builder version 2021.1.2, it was successfully uploading the experiment under that version, but then I upgraded to 2021.2.3 (the latest version, I suppose), made some minor changes in the experiment and tried to upload it to pavlovia. no chance so far.

any suggestions?

thanks in advance, t

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