Ambisonic FX channel vs surround; why do no vst inserts work?

I have been for a long time, using a 6.0 surround channel for fx and assigning a stereo effect to eg 1&2 then a diff one to 3&4 and so on so that I can use the send panner to position in these effects.
I am wanting to expand this channel output so that I can use 8 channels or more and subsequently have 4 fx and be able to use the ambisonic panner.
So I set up an ambisonic 2nd order but now none of the fx are respecting any routing overrides and register nothing when I insert…if it works for surround then why does it not work for a mulit channel amisonic channel?