DIAGNOSIS Yeah, this one's common. The brushroll motor in the SEB 228 powerhead has either overheated (triggering its thermal cutoff) or the drive belt has snapped or slipped off. The green light just means it's getting power, not that the roller motor is happy.
FIX First, unplug everything. Flip the powerhead over and remove the soleplate (usually a few Phillips-head screws). Inspect the belt. If it's broken, stretched to oblivion, or off its pulley, that's your culprit. Replacement belts are a standard part. If the belt looks fine, the motor might have overheated. Let the whole unit cool down for an hour in case the thermal fuse needs to reset.
IF THAT DIDN'T WORK The issue could be a failed brushroll motor or a problem with the electrical connection in the wand. Try the powerhead on a different compatible Miele hose/wand if you have one, to rule out a fault in the power delivery from the handle.
HEADS UP Always clear hair and string from the brushroll ends before it winds so tight it stalls the motor and kills the belt. Doing this monthly saves a lot of headaches.