Read manual very carefully and check the motor jumper.
Purchased to replace an older version as fixing and inlet were identical, followed installation instructions (not included with unit, had to view online) but did not work, eventually found a jumper on the motor board was in the on position, think this must be an error as when the jumper is in the on position the motor is off, put the jumper in the off position and the motor works and we get hot water.
Also this item was a "Grey import" from Ireland, although sold in the UK but is compatible with UK plumbing and wiring.
Verified purchase: YesCondition: New