REST iissue

I purchase membership from https://idxrealtypro.com and installed IDX Realty Pro wp plugin from here https://wordpress.org/plugins/realty-idx-pro/ but I am not able to configure it because of RETS server. Its showing an error message http://prntscr.com/jzso69

Also I search for videos on youtube and I see there is a RETS button here http://prntscr.com/jzsp5d. But in case of mine nothing is appearing. Please help.