Panasonic dvr not recognising aerial

I have a panasonic dvr,( it does not have freeview built in).I have just connected it to a new 55 " sony lcd tv via a scart lead in “av1” - I only have 1 scart connection at the rear of the tv. When I switch on the dvr, I can access the menu, and even play previously recorded video recorded through old tv, however when I try to “auto tune” it gives me an error message saying “no channels found” and “check aerial connection”. I have the aerial going directly to the dvr, and a loop connection from the tv to the dvr, this set up always worked previously with the smaller 40" sony tv so why is it not working now? Is it something to do with settings within the dvr or smart tv?