Unable to Boot into SwitchOS on CRS354-48G-4S+2Q+ - Kernel Cannot Be Loaded

Maybe (or not) some added info:
http://forum.mikrotik.com/t/swos-on-crs354-48g-4s-2q-missing/137340/1

Initially SWOS was not available for this model.
But later SW versions did make it available.

Down in the thread is maybe the solution to your problem:

Worth to try …