Oh no! Well if you're at the VERY end, if you just went through a really big fight, something was supposed to happen during that fight to open the door. I also made an enemy drop a key in case the door didn't open on its own. It's possible the game bugged out somehow in the process of all of this and things didn't trigger properly. I'll explain the end here so maybe you can tell me what happened at what part:

You find a secret door which leads back into the main dungeon. A locked door is in front of you. You follow a long winding path, fighting a veteran guard along the way. The path ends with a small room containing a chest with a note inside. Reading the note, you realize you've been set up. As you leave, you are ambushed, and 6 rounds into the fight (or 36 seconds later, if the fight ends too soon), that first locked door opens and more guards rush in. When they are all dead, you have won the map and leave through the now-open door.

Thanks for the reply! I got to the last area and killed the vet guard. Opened all the "secret" doors. Opened the little room and chest, and read the note. Nothing happened. No guards no fight.

That's interesting...you were not supposed to be able to open the secret doors. In fact I set the DC for finding them much higher than the DM normally allows, I think I set it at 50? How did you detect them? The reason there were no guards to fight is because after reading the note, you are meant to walk backwards along the corridor and be surprised when all the doors open at once. I bet the guards didn't spawn because you already had the doors open and were able to just walk directly south and therefore didn't have to step on the specific trigger that opened them all and started the fight. It's up in that hallway across from the chest.