Had an earlier version of this may years ago.
Check if the drum shutters are open and make sure they are closed properly.
Check to see if there is anything jamming the drum. On my old machine the agitator paddles inside were clip on plastic parts that could be removed to access the space between drum and housing to let you check. (Bit of a faff: close the drum shutter, rotate the drum by hand until the back of the agitator is visible and push the locating lug in and slide the paddle out, allowing it to drop into the drum. BEWARE OF SHARP EDGES ON THE DRUM!
Alternatively, it may be a problem with the drive system - accessible from underneath.
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October 2017