It’s generally considered to be a good time to clean out hog houses at the moment. More information: https://www.hedgehogstreet.org/cleaning-out-boxes/
You really need to check, first, whether there are any hogs in residence. If you don’t have cameras, (and even if you do, it’s worth a double check – hogs are very clever at timing their activities in the time gaps between clips or images) try putting a twig, or rolled up bit of paper in the doorway to see whether it’s moved. Some hogs seem to keep using the boxes when we hope they wouldn’t be! But if there is a hog in there, you shouldn’t disturb it.
You do really need to clean out the boxes with boiling water (rather than just change bedding) because there are often parasite eggs left in the gaps between joints in the wood, etc.
I would just put a small amount of bedding in, to give them the idea, and leave a supply nearby. Many hogs like to do their own interior decorations.
Hopefully some hogs will move back in again soon.
Good luck and happy hog watching.