We looked on-line and found that 66% of the time the thermal fuse was the problem, so we ordered and replaced the fuse.
That did not solve the problem. More looking on the internet found that the dishwasher has a sales mode that prevents it from starting. We had never heard of the sales mode previously. We followed the instructions for turning off the sales mode by sequentially pressing 2 buttons. The dishwasher then worked normally.