Peel and Stick Tiles Coming Off

My husband has used these in homes and he puts adhesive on the floor anyway, so that dirt can't get down thru the edge of each tile that will eventually make the tile come up. Never had to do a repair of them due to doing this.

You don't say what the material is that the tiles are adhering to. However, if it not a porous material then I would lift up the tiles that are not sticking being careful not to break or tear them. Clean off the old adhesive and apply contact adhesive. With contactadhesive you have to wait a period of time before applying to the substrate. The directions on the can should give you that information.