Varnish issue

Hello everybody!

I have recently migrated all my sites to a new server

These were working fine, until I installed Varnish

And now there are some wordpress sites that I can’t log in and some that work just fine!

I have tried multiple varnish configuration files, and it keeps failing. SAdly it only shows me a blank page, or sometimes in Chrome it says ERR_INCOMPLETE_CHUNKED_ENCODING

Thanks in advance!

The page I need help with: [log in to see the link]