Paulz,
I am glad that your Tyros is alive again! As the reset did not work the first time, I don’t think it was the reset that solved the issue. My guess is rather that your keyboard was suffering from static electricity and by waiting one or a few days, the problem solved itself (technical view: an electric charge on the internal capacitors prevented your device from starting up and by waiting some time, the charge disappeared due to leakage current and maybe also due to the fact that from time to time your pressed the power button). This is only a personal guess but most important is that the issue is solved.
Johan