AWS CloudFront problem with site forms

Hi,

I have a password protected site which is a copy of my production site. I am doing some tests connecting an AWS CloudFront distribution in order to test IP filtering rules. By now my distribution is bare with no WAF rules and in general the website works fine behind CF but I'm stuck with 401 error in forms submission. I have tested with different policies and the result is the same. I wonder if errors have to do with the "Password protected" configuration. Any idea?