That would be my first guess... The fuse is not buried very deep in the transformer. Simply unwind the outer windings until you reach the inline fuse, replace and rewind. It's about as difficult as sowing a button to a shirt, but you will have to be patient, it takes (a lot) of time. A new transformer is still available as replacement part...
Fuses however, open for a reason, better find the reason before you plug it in again
1) external: intermittent connection to mains (check cables, wall outlet, etc.) or overvoltage
2) internal: Genelec uses quality components, but given their age and the heat buildup, some of the caps will have dried out.