I understand that the belief in qualia may be based on a sensual illusion, but I can't get my head around illusionism and struggling to state what I mean.

For the illusion of qualia to be experienced - and I do seem to experience something, either qualia or their illusion - not just believe I do - rather than stated etc. there must definitely be qualia.

I suppose illusionists think that the "illusion" is just cognitive and we are not tricked into having illusory experiences: we do not seem to have experiences (we just have the mistaken belief we do).

But that seems completely impossible.