Deposits from multi-unit owners

We have a gentleman in our park that owns 3 houses and rents them out. The previous manager went behind the old owners back and helped this guy get these houses. We bought the park a couple of months ago and have billed him for a deposit on the 3 houses, he doesn’t want to pay it and I don’t know if we should just let it go or push the issue.Thanks,Leighnae