You might want to read through this.
" Ceramic Input Capacitors Can Cause Overvoltage Transients"
"To illustrate the problem, a typical 24V wall adapter used in notebook computer applications was connected to the input of a typical notebook computer DC/DC converter.
The DC/DC converter used was a synchronous buck
converter that generates 3.3V from a 24V input."
Quickly turning on and off an SMPS can be a brutal test. If you have a scope cycle the input power to the board and view the input waveform, once you get it to work.