Why can't I get Rested or Well Rested?

I sleep in rented beds and my bed in Jorrvaskr (with the Companions) and no matter how long I sleep I don't get the notification that I'm rested or well rested anymore.

I've looked at my active effects to check for Lycanthropy or Vampirism and all I have are positive effects.

I have slept in rented beds immediately after receiving blessings and having all diseases cured at the shrine of Mara.

What are other reasons I might not be able to get rested or well rested?

You've got the Lover's Stone active.

It doesn't stack with the Rested / Well Rested / Lover's Comfort effects.

One of the effects of being a Werewolf is

Beast Blood Becoming a Werewolf bestows the Beast Blood ability, which grants a 100% resistance to all diseases in both human and beast forms, but disallows you to acquire resting bonuses.

as noted here.

Beast Blood is listed as a positive effect under Active Effects for its 100% Resistance to Disease but the lack of restful sleep is an unlisted side effect.

One of the possible bugs found after being cured is not receiving the well rested status as described in this post.

Fixes to the bug are described in that post and under the Cure section found here

Another possibility might be that you have the Lover Stone Active Effect. You cannot get the Well Rested Effect if you already have the bonus from the Stone as noted both in this section describing sleep and in this section under "Notes" for the Stone's effect.

I had the same problem (never being able to get any type of "rested" bonus) and discovered that was a stuck quest called PlayerSleepQuest.

Since nearly every scripted activity in Skyrim is a "quest" of some sort (at least internally), it's possible that a previous execution of the script did not complete properly; I've found this can happen from a crash or even using "qqq" from the command shell to fast-quit. Additionally, you can only have one instance of any given quest active at a time.

Luckily the solution is pretty simple:

1. From your current game, use the ~ key to enter the command console.
2. Type help PlayerSleepQuest to get the questID. It should be 000FC1A2, but if your's is different for some odd reason, then be sure to use whatever ID is shown for the remaining steps.
3. Type stopquest 000FC1A2 (press Enter)
4. Type resetquest 000FC1A2 (press Enter)

The next time you sleep, the PlayerSleepQuest should activate properly and provide the appropriate feedback on screen and be shown in your active powers list.

(Disclaimer: I have absolutely no idea how doing this might interact with any currently active Lycanthropy or Vampirism character state! Be sure to have a good/known save to revert to should things go haywire!)