What to do if our landlord returned our deposit on a commercial rental but now will not let us get our property out saying things needs fixing?

No, a landlord may NOT keep your belongings or property. If there is damage which the landlord discovers ro which he may properly charge you , then if either the damage exceeds the deposit, or the landlord returned the deposit prior to discovering the damage, his proper recourse is to sue you for the money you owe. He has no right to hold onto your belongings unless you had actually provided them as collateral for the obligation to pay for repairs. You could contact the police--in theory, they should help you, since the landlord is unlawfully holding your property. If they decline to get involved, characterizing this as a civil landlord-tenant dispute, you would bring a legal action on an "emergent" (or urgent) basis, seeking a court order that the lanldord return your belongings.