For authentication with facebook, ngrok is refused by facebook
consider as a malicious domain therefore does not work WHAT TO DO IN THIS CASE?
I would reach out to Ngrox or Facebook support to see what they suggest around this area.
one thing you can try when you start ngrok is to start it with region
ngrok http 8000 --region us
as an example though change region, port and http/https as needed see if that works.
Super thank you very much when I tried with the us region and I resubmitted it worked
Glad you got it sorted happy to help 
shared pleasure