I agree, it is frustrating. I have a hogilo too, and don’t think it has been much used, although it is under a bush and hidden by a lot of vegetation so it’s difficult to be sure.
I wonder, though, whether part of the problem with yours is that it is too near to the feeding station. Females in particular would probably want to pick somewhere where they are less likely to be disturbed by other hogs.
Having said that, I had one of my boxes for about 2 years – mostly used for putting food in – before a hog decided to make a nest in it and maybe it just takes a while for them to ‘accept it’ or for it to smell right. I think the results of the hedgehog houses survey are supposed to be out around now. Maybe that will throw some more light on things.