i worked with the BOS and wiped out the underground railroad, probably a bit too early on to be doin that and now i cant get into ticonderoga the elevator wont work and the door upstairs requires a terminal from downstairs from the elevator i believe is there any way around this please, im trying to get the guns and ammo mag up there

If I recall he has to let you in whenever you want to go up so if he is dead or in hiding he can't let you in anymore. If that is the case then another kudos to Bethesda for choices and consequences.

If you are on PC you could just try "tlc" in the console.

nah on xbox one