All 3 fuses ?
You have 1 in the plug
Another one by the switch and 2 in the amp board.
Check the the one by the switch is not blown.
If all checks OK measure with a voltmeter if you have AC on the fuses in the Amp board.
Cambridge Audio amps are no party amps they just don't have enough heatsink for the power transistors.
I had (still do) an HK6500 integrated amp that stopped working one night (playng loud). As it turns out HK eschewed the notion of fuses and put a small gauge turn of wire on the primary of the transformer: the $75.00 transformer was used in place of a $0.50 fuse.
I had measured it the transformer via the AC connector and it was open. There were no other components in the way. Luckily the dealer was embarassed by this and managed to get it repaired under warranty....