Just bought a gently used Royal M2028 Classic Upright. Beater brush does not turn and I am assuming the belt is broken. How do you put a new one on?

SOURCE: Royal upright handle fork spring replacement

This is actually fairly normal, and there's no real easy way to get that bolt out. Your best bet is to continue turning it as if you were unscrewing it while applying pressure to the opposite end. A narrow piece of metal can help, especially if coaxed with a ballpeen hammer. If possible, you can try to apply some pressure upward on the spring to keep it from holding the bolt too tightly, but this only works about half the time.
Getting the bolt back into place is also something of a nightmare, as you have to use your thumbs to hold the new spring in place while forcing the bolt back into place. I've had indentations on my thumbs from holding that spring many times.

Good luck,

-R

SOURCE: directions for Bissell upright rug shampoo vacuum

need belt on brush

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: 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: Problems with Royal 4000 Classic Bagged Upright Vacuum?

Try this site.
https://www.2instructions.com/search.php?cmarque=ROYAL&modele=4000%20CLASSIC