Hi I'm having the same issue - although if I leave it half an hour or so, it allows me to switch it back on. And then it's either picked up where it left off or let's me start a new wash from the start.
I've done the basic checks:
-> power - check that the socket works with other devices
-> filter - check the filter in the front is not blocked (note that you might have to drain the tub first if it's stopped and has a lot of water. There are lots of instructions to do this, basically get a shallow bucket, pull out the black hose and take the top off it, it will drain into the bucket). Then you can take out the filter and clean it
-> drain hose - check whether the hose is blocked. Mine was full of gunk so likely it's been switching off after about 15 mins through the cycle when it tries to drain and can't. I'm going to try and replace the drain hose and see if that works.
-> run the cleaning cycle/very hot wash cycle - I would imagine that a 90C cycle would clean out the drain hose if anything would. I have been doing the eco-clean cycle every once in a while but would imagine once a month would be advisable to keep the drain hose from filling with gunk.
-> run a few rinse/drain cycles - if yours has the option and it does switch back on again, you can try running a rinse and drain cycle as this will also check whether your drain pump is working
