Assuming you have the digital pump in the loft, some of those were a faulty batch and are replaced free of charge if you have a service contract. Mine behaved just like yours, and the man came out, Chris from Aqualisa, top bloke btw, and interrogated it on his laptop, saw it had over 1000 restarts or something, and just fitted a new pump and all was well.
If you have the push button in the shower with a blue ring led round it, is this dim? If so, it's worth taking the button assembly apart and cleaning it and the contacts on the push-fit cable connector. If the led is brighter thereafter and the shower works ok, that's a simple fix.