Try all of the above. But curious.. are all the beds in the same room? Is the bed shared? Were they able to get to their beds previously?
If suggestions above do not work I would suggest removing everything from that room including the flooring. Something is "hidden" in there and blocking access to the bed. I had to remove an entire kitchen once and part of a hallway before I found an almost invisible object embedded in a corner.
Another possibility is social jigs
The game creates a temporary object when two Sims interact with each other. These are SocialJigs are created so animals and other sims can not come between two interacting sims. Once the sims finish the interactions these objects should be cleared out but it does not always happen. Some jigs are visible (they look like ovals or small balls), others are not.
Visible SocialJigs can easily be deleted with Move Objects.
Jigs that are not visible need to be removed with a mod.
You can check this in Master Controller by clicking on City Hall and accessing NRAAS -> Master Controller -> City -> Object Statistics
If you see two party social jigs in there select them and accept to flush the object.