Brush/beater bar does not spin. - Riccar 8850 Vacuum

SOURCE: beater brush won't spin but belt is intact and ok.

For your beater brush to spin, you have to meet two conditions:
1) the vacuum cleaner has to be reclined (put your foot on the front and pull back on the handle).
2) The clutch actuator (the dial where you switch between BEAR FLOORS and CARPETS needs to be set to CARPETS).

If the brushbar/beater bar still doesn't spin after that, call the Dyson helpline, they will assist you. If you are saying that the brushbar isn't spinning because it is not picking up any dirt, you may have a loose internal hose, a blockage in the machine or the bristles on the brushbar are worn. Call the Dyson helpline for assistance.

SOURCE: brush bar not spinning

Depending on the make and model the belt may be bad or if it has a clutch assembly then it has gone bad.

SOURCE: the beater bar/brush won't turn

HI THERE,
FIRSTLY, REMOVE SOLEPALTE BY QUARTER TURNING THE 3 COLOURED STUDS,THEN CHECK TO SEE IF THERE IS ANYTHING OBSTRUCTING THE BRUSH BAR OR IF THE BELT IS WORN OR SNAPPED. IF ALL SEEMS WELL PUT THE SOLEPLATE BACK ON AND ENSURE CLUTCH IS ENGAGED TO AUTO AND TRY IT AGAIN. IF NO JOY THEN PLEASE COME BACK TO ME.
REGARDS
DAZ

SOURCE: My Dyson Animal 14 beater brush will not turn.

It MAY be a clutch issue. I had a similar problem with my DC07 Animal recently a posted a solution elsewhere on this site, but here's the summary. To reset the clutch on my model, recline the vacuum, turn it on it's side and slowly change the carpet/bare floor knob from one setting to the other about 6 times. This apparently reset the clutch and now it works fine. You may also wish to call DYSON. They're very helpful and walk you through troubleshooting before recommending servicing. Their number is 1-866-693-9766. They'll need your model and serial number (located on bottom of uinit).

SOURCE: Bissell Beater brush sporadic

I was having the same problem with my Healthy Home vac and happened to read a solution to another question on this site posted by someone with the user name "9008". I followed his suggestion and my vac works great again. There is a screw on the back of the handle near the cord holders that can loosen up over time. When this screw is loose, the brush switch (and therefore the brushes) do not work properly. I'm not sure why this little screw causes such a big problem, but it does. To find this screw, look on the back of the handle, it's on the edge, kind of behind the hose. You should see a triangle with a Phillips screw-head symbol embossed in the plastic. Tighten this screw gently (careful not to over-tighten and strip it!). Also, not a bad idea to tighten the other screws...I found many of mine to be quite loose. Hope this helps!!