Chocolate Cake

Either there is a bug in the game or I am overlooking something stupidly obvious, but the oversized green spider outside of the library in Caerworn castle won't recognize that the chocolate cake is in my inventory. I successfully found the cook's spoon, the Sheets quest is in my missions, and I have even completed a number of other quests in the module. The icon for the cake is a chest, so I thought perhaps it needed to be unlocked at a locksmith but that did not work either. It has become a bit frustrating. Any help would be greatly appreciated.

You need Persuasion of at least 90 and the quest Token of Friendship: For Old Shaman, give the ghost of Lord John Sheets, Caerworn Castle, a token of friendship, a sack of rare pink chocolates.

Thank you for the help. I didn't have high enough persuasion. A quick fortify potion solved the problem.