copper key?

[LordAdeds]

anyone have it bug out while trying to use the copper key in the mines? had one with me from floor 1 to the chest room but it then tells me I have to have prior floors unlocked? went from floor 1 - 10 twice and had the same bug happen.

[Bob Loblaw]

You have to unlock every prior level with the appropriate key. i.e. every single level needs its own copper key to unlock permanently (from 0-10).

[Caelestus]

Did you use a rusty key to unlock a previous floor?

[Willow Rivers]

You cannot use rusty keys then use a copper on the last gate. Every single gate has to be permanently opened with a copper key to progress.