Gaaaaaaaa. Can't hear inserts (including tuner) on record

This is driving me nuts. Was about to put down a bass guitar part on a soundtrack I’m doing. Lazy option, why not use the Steinberg tuner? Insert it into the audio track, enable monitoring. Nothing. I can hear audio but the tuner isn’t seeing anythingt. Same thing from inserting it into the actual input channel. In fact, after further wasting time, I find that I could insert anything I like into any of them, and I cannot hear the inserts. Ah! Maybe try unchecking ‘enable direct monitoring’! Nope. Nothing.

What magic tiny button or check box have I accidentally pressed or checked that does this? Or is it a flaw/bug?

Using an RME BabyFace Pro. There is currently no direct monitoring set up within TotalMixFX.

I can hear the clean audio, but the inserts on either the input channel or the audio channel are not in the signal path.

As an aside, if Steinberg were to re-write their whole settings and preferences menus in an actual logical form, that would be more helpful than any feature upgrade. It has been an absolute mess as long as I’ve used the software (since Cubase SX)