The real estate agent will welcome you into the building and will automatically say something like “I see you have a deed” or something like that, and provide prompts for you to follow. Drop the deed directly onto him as if you were initiating a transfer of an item with anyone in game and he’ll take it and credit it back into your account. For extra security use the one in Occlo as he’s been made static and won’t walk away the second you take your finger off the mouse resulting in you dropping a fort deed on the floor.
Save your chat logs from the NPC - page a GM & double check that a cheque isn’t lurking somewhere in your bank box. Can you check your chat log and see what he said after you dropped the deed on him?