the older V boxes had a toggle setting somewhere , where you choose between: use scart / use HDMi
so you had to connect on scart, then flip that setting...
frankly - you'd be better advised to insist on an engineer visit with a newer box and have him set that up for HDMi
the next TV set you buy will probably not have a scart input !
the only reason to stay on the old box will be to watch existing recordings, that cannot be copied over.
setting HDMi to 1080p is correct only you have a full HD 1080 TV, you could try setting that to 720, if unsure, or to auto if there is an auto option
a " HD ready" TV supports 720, a "full HD" TV supports 1080