Forgot to mention (if it's not obvious from the title, this is for LBA 1, not 2). Haven't got around to playing 2 yet, so no idea!

There may be some spoilers here, kind of unnavoidable. Sorry. If you don't want to have any spoilers, don't read any further than this.

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Okay, I've done what I can assume is a fair bit of the game, am a level 4 magic wielder person, have the dino-fly and am now back on Principal island, trying to get the plans for the teleportation base. I kill the guard in the trench behind the wire, talked to the elephant prisoner, climbed up the ladder and killed the two red elephant guards.
Opened the gate with the card and killed the robobunny guard. I then killed the elephant nurse that teleports in and pick up the key that he drops to let you into the base.
Going up to the bases doors however the key gets used up, but the doors don't open.
Has this happened for anyone else?

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EDIT 2:
Nevermind, solved.
My google-fu was weak first time around.
Anyone else gets this - just open holomap.

--Yours was the first post I saw with the fix--thanks! I had exactly the same problem.

I just got up to this point in the game now

so just open up the holomap to fix it?

Yeah, just opening and closing the holomap worked for me.