I too have sent many hairpieces in to have reconditioned and they really do an awesome job.
But, the last couple of units I had done I did experienced the exact same problem, nothing would stick to it... Now this is what I did that got me through the problem... I washed and dryed the unit and I took blue lace tape and put around the perimeter. I took a blow dryer (On hot) and heated the tape on the unit. I left the tape on the unit overnight and in the morning I used 99% alcohol to remove the tape... I rewashed the unit and attached it without any problems.
Of course the real solution would be for the factory to stop spraying whatever it is their spraying on the units.