There has been a long-standing bug where I'm alone on the server and unable to skip the night by sleeping (the player just lays there indefinitely).
I have a theory as to why this is happening: if you are marked as AFK when the only other player leaves, the AFK mechanism will no longer function (I assume it is disabled while alone), but you remain in an AFK state according to other mechanics (such as sleeping), so you are no longer able to skip nights until you relog.