ADFS setup for CRM2016 (on-premise)

We have two servers, one for ADFS and one for CRM2016. We need to set up an IFD. We have done everything as per instruction and it works except one problem. When we hit the internal url from Intranet the authentication popup is shown. Which is wrong. Even when we try to login through this popup it redirects correctly to our ADFS but shows a page not found error. We have added everything to intranet zone(IE->InternetOption) We need a guy with previous experience to fix this issue. External URL is working fine