Hi welcome to our forum. At the very basic level you just need to connect a aerial to the box and a hdmi cable to the TV. Adding an aerial connection from the box RF out to the TV requires you to turn off power saving in sby if you want to use the TV’s own tuners while the box is in sby.
First thing to try is disconnect the power from the box and leave it for say 5 mins. Hopefully your recordings will appear again. Let us know how you get on.
Internet connection is only required for catch up services.