Did you use stainless or alu riv nuts?My Norco frame is solid no thin ali.
For any one needing to tighten or fit new ones you will need a M5 bolt, a M6 nut or bigger and a washer.
Place the washer against the riv nut then the M6 nut then pass the M5 bolt through them and thread in to the riv nut, hold the M6 nut with a spanner and use an allen key to tighten the bolt which will compress the riv nut you will feel it tightening as you wind the allen key around.