trailer brake problems

Hey guys i have a 08 puma with a tandem axle trailer and single axle brakes. since i bought the boat the trailer brakes have not worked so i decided to try to get them up and running again. both calipers are good and pads are new. i found a tear in the rubber brake line where the swing tongue opens and closes so i replaced that. I inspected all the other lines and everything looks good. The problem im having is im getting no brake pressure when bleeding the brakes. I hooked up a vacuum bleeder to get some fluid running thru the system and that works fine i ran a few ounces thru both sides to flush out any crud in th system and all is well but when i go to bleed them like i said im getting no pressure. Also i couldnt get fluid to flow thru the system until i hooked the plug up to my truck and put it into reverse im guessing the back up solenoid is closed and when power is applied it opens up. So i stuck a screwdriver thru the access hole and kept the manual release pushed in and cranked away on the plunger and i cant get it to build pressure or get any fluid to come out when i have someone crack the bleeder. I have done a few other trailers and did not have any problems so im a little stumped here. Is it possible my master cylinder is shot and thats why im not getting any pressure? Its not leaking anywhere i can see just wondering if this could possibly be my problem. Also when i was vacuum bleeding it i could get plenty of fluid to come thru but the air bubbles never stopped so its gotta be sucking air in somewhere but like i said i cant see any leaks anywhere. also does power need to be supplied to the solenoid when bleeding? i dont recall having to do this to other trailers but i tried it both ways and didnt make a difference. thanks guys!!