Skis were running when dropped off at shop to winterize, then when I picked them up to use them this season - nothing, no beep, no cranking absolutely nothing. The company that winterized them epoxyed battery tenders inside the hull, attached them to the batterys but did not plug them into power. I tried to jump them but after hooking up jumper cables, still no beep after putting on the lanyard key. Charged the batteries, but still NOTHING. Any suggestions where to start? Thanks for any and all advice!