ooo
One more thing that's very important & I missed saying earlier, only thought of it last night lol
If you're previous board worked and you're new one doesn’t, and you have
not added any wiring to the set-up that might be dodge, it could be this...
In you're board is a split load...Assuming it's a split load, e.g. 2 neutral bar's, you must keep the neutral's from each bar separate
This is to say the Live cables on the Non-RCD side of the board,
must have there associated neutral's on the NON-RCD side neutral bar, and the same for the RCD side, keep the lives & neutral’s from protected circuit’s on that side of the board only
I would strongly suggest that you isolate the board, remove cover, check inside the cables one by one, check the first live cable, then find it's neutral and make sure it's in the same side as the MCB...do this for them all and see if you can find the problem
One of the very first mistakes I made with a split-load was to have a neutral in the wrong block, genuine mistake if you're tired and underfed
Good luck!!