DIAGNOSIS Power isn’t getting from the wand to the cleaner head. This is either because the electrical contacts are dirty/corroded, the head is mechanically jammed, or there’s a fault in the connection.
FIX Start with the jam. Detach the cleaner head and check for a massive hair wrap around the brush bar ends, locking it up. Clear it as described in other fixes. If it spins freely by hand, check the contacts. Look at the metal pins on the end of the wand and the corresponding slots on the cleaner head. Use a dry cotton swab to clean any dust or debris off them. Then, reattach the head, making sure it clicks firmly into place.
IF THAT DIDN’T WORK Test the wand with the main vacuum. Does the vacuum run with *just* the wand attached (no head)? If it does, the wand is good. The problem is likely in the cleaner head’s internal drive motor. These aren’t user-serviceable. You’d need to replace the cleaner head assembly.
HEADS UP This often happens after vacuuming up a long string or hair tie that instantly jams the brush bar. Always do a quick visual check of the area for large stringy objects before you vacuum.