Wet it thoroughly and see if that helps. When I had mice they were just trying to find a nice comfortable place to nest. Left right away once it was no longer dry,althoifg mind, this was in colder seasons. Hope this helps, no guarantees.

I don't think you can mouse-proof a bin. It needs air holes for the compost process to work, and that means small vermin can get in. If you can, locate the bin away from your house to prevent the problem from spreading there, but otherwise I think you need to make peace with the fact that some mice will take refuge there. Keep it just to leaves (no household scraps) and the vermin shouldn't be bad. At least you aren't feeding them, just giving them some shelter.

The solution to no vermin is an elevated compost tumbler - which is expensive for a good one, and cheap ones fall apart after a year or two or aren't big enough to actually compost anything. But that's what I recommend for people in the city where rats are a problem.

I had the same problem in my urban yard at my last house. Building a "mouse proof' structure for my compost bin was how my now husband won my heart while we were courting. Here's a photo. It doubled as a trellis upon which to stake raspberries. The bottom was a plywood raised base, to keep the mousies from burrowing into it. That was their main entry point. The rest was to hide it/make it look more attractive in the tiny space of my row house yard.

I pink, I would fall in love with him too if he built that for me!

Anilix, rodents can fit in a space as small as their head! So hardware cloth will help, but you have to be mindful of other openings.

When I was out in the country, I moved my compost operation away from the house, and eventually found hawks and even owls perched on out fence waiting for a meal......no more mice/rats!

Now that I'm in town, where there are rats, I try to avoid putting household waste into my compost. I also use sound emitters around my garden.