This happens to me all the time, and I usually have to ask the FAs to use the awkward under-seat reset button - but on my most recent flight, the FA fixed it by pressing "lumbar +" three times and then "cushion +" once. A minute later, and it was all inflated again! I did that combination myself later in the flight when it failed again and it worked great. She said techops showed it to her, and that it's a 'factory reset' option. The seat stays powered on the whole time, so I don't think it's an actual electrical reset.