Pavlovia opens empty window

Win10
PsychoPy version : v3.0.0b11
Standard Standalone? (y/n) : yes
What are you trying to achieve?: I want to run my experiment online

What did you try to make it work?:
I uploaded it to Pavlovia. I’ve tried to open Stroop demo and it worked.

What specifically went wrong when you tried that?:
An empty window in browser opens and nothing happens.
And there’s also this line in output:
return codecs.charmap_decode(input,self.errors,decoding_table)[0]
UnicodeDecodeError: ‘charmap’ codec can’t decode byte 0x98 in position 5850: character maps to