Last chest won't open

[MaxieFox]

me and my friend have found all 4 chests and yet we still cannot open the last chest.
we found the 1 in heiberheim, Cyseal, next to the wizard house in phantom forest and the 1 on the portal puzzle. yet when we talk to the last chest she just screams "I AM THE LAST CHEST, THE LAST CHEST" anyone know what we're doing wrong? thanks :)

[Sarval-James 540]

Did you read letters within them?By reading this you acquire code one number from each chest,and then ypou should type in it during convesation with the Last Chest.Be worried in letters appropriate digit hidden with litlle enigma.

[MaxieFox]

Yeah we got the code and answerd the riddles, should we just type the code whilst in conversation with the last chest? like the default thing she says?

[rn_archl0rd]

Is one of the main characters holding all the letters and trying to open the chest or are you using a companion to open it?