Stuck on Memories of Eliza - Eliza's Small Treasure Chest and key

[MTie]

I have both the treasure chest and the jail key (stolen from Tatar again) in my inventory, but when I put them next to each other, I can't combine them. The little + does not appear. I have forfeited the quest 2 or 3 times, threw away both chest and key, got them for the second or third time. No difference. Even restarted the game, used different server etc. They still won't combine.
Is this a general problem or I am still doing something wrong?

[MTie]

Well, I have no idea what happened. I gave up on the quest and went fishing. At some point I opened my inventory and tried again and suddenly the two could combine and I am no longer stuck!

[Shealah]

I had exactly the same thing, I could not combine those 2 items. It helped when I placed them above in my invent After a long loooong long! time I could go on.

[KCrow]

You have to place them next to each other in your inventory and a small plus sign will appear on one of the items so you can combine them... I know I'm about a year behind on this for you but just in case you never did figure it out.