Lamona HJA8362 empties too soon

I am trying to sort out my daughter’s Lamona HJA8362 dishwasher which she has had for about 4 years. She used it but the dishes hadn’t cleaned so thinking she had forgotten the tablet she set it again – same result but she noticed a weird smell of
burnt lemons! I looked at it and noticed there was not enough pressure on the water to spin the top arms, so checked a few things from your forum. Machine/arms ect very
clean, motor/pump appears to be working but found that machine fills up with hot
water but then empties, having made no attempt to wash. (this is when the smell comes as heater is still on) Can anybody suggest what may be causing this?