Mine did the same thing on both sides. I bought some DAP Contact Cement $12 from Home Depot and put on mine. Works like a charm!!!! Just go by the instructions on the DAP can. It's extremely easy to do/use. This is the same stuff that Hydro-Turf recommends to use with their mats.
mine are doing to same I tried re-cleaning and used wellwood adhesive it didn't work that good some edges are not sticking..i think the plastic needs ruffed up so it has something to stick to since it is to smooth.