Had no trouble cleansing Earth Stone. Slept at home (Severin) and woke up at Sun Stone. Tried Bend Will 3 times. No luck. Stone not cleansed.
Suggestions?

Reload a Save from before allowing Your character to sleep. I had the same issue from sleeping on Solstiem.

TBH I was so paranoid about sleep walking Miraak style that my character didn't even sleep for three or four days till all but the tree and water stone were cleansed. Expected to wake up at the WS but had to travel there, no prob. Hit it, cleansed it and now waiting for the finale.