Need help with Ny'Alotha/N'Zoth the Corruptor mechanics

Title ... I (believe!) I have more than enough ilvl to solo N'Zoth the Corruptor, but seem to get tripped up over mechanics and get one-shot.

I can easily phase to Psychus and quickly kill him, but the issue (I think) is phasing (is that the right term?) back to be able to dps N'Zoth (for 30 seconds?).

My understanding is that once you kill Psychus you have to stand (or click?) your body - where I believe that takes the form of a Severed Consciousness. But I can't seem to reliably click on it ... it appears as a gear but ... I can't seem to click, activate it or whatever and die soon after.

Here and there I seem to make it back to be able to dps N'zoth, and get it down to less than half, transition back to kill tentacles, phase to Psychus again, kill it and then can't reliably phase to a point where I can dps N'zoth (somehow I failed to click my character/Severed Consciousness/whatever).

Watching videos and such doesn't seem to help ... I can't find the detail of what I'm missing.

Thoughts?

Thanks!!