Thank you for your reply. My problem is, I can't seem to use my bed in the castle. Does the ability to use my bed become available upon completion of a specific quest?
No, there isn't a requirement to use or unlock the bed. :D
Maybe you're interacting with the wrong spot? You need to interact with the bottom end of the bed.
When you take the big blue stairs up from the throne room, Ryen's room is directly north of the stairs on the map of the sleeping chambers.
I took your advice and just started interacting with it from everywhere. Found a spot in the bottom-left corner that worked 🤣 Thanks!