All sounds good with the 90 powering the 62, with the SNAIC4 in the NAC’s 4-pin output going to the NAP’s 4-pin input. The 5-pin plug installed.
With the Olive flatcap, added the SNAIC5 at the 62, after removing the 5-pin plug obviously . Ran it to the flatcap’s fourth din input (the only 5-pin socket).
Ran the SNAIC4 from the flatcap’s third output (4-pin) to the NAP90’s 4-pin input.
It reads as though you’ve connected correctly, but just to confirm: there should be no direct connection between the 62 and 90 when using the Flatcap.
I would turn it all off and check that the Snaic 5 is correctly wired at its Din plugs, just in case an earth connection has broken. It’s the only new wire in the setup so maybe at fault. If it looks ok, it may be worth borrowing another just to try and be sure.