Yes the question is a little bit vague, because I can not imagine, how you can come to a situation,
that you managed to enable the 1st mic but not the second, as its the same from the steps.

Maybe you should consult the fine manual, esp. chapter 9.6.

Basic stuff: you will read in the manual, that the breakout cable provides you 2 XLR inputs
that can be used for both, Mic and also as Line input (if you set it to 0dB).

So, to connect your 2nd Mic to "Analog 2 IN" isn't the issue, right ?! OK, next thing.

In TM FX you have in the upper row the Hardware Inputs. Analog 1 and Analog 2 is for connecting Mic/Line/Instr.
Usually these two channels are combined as Stereo channel, see pic in the handbook chapter 9.6, page 21.
Click to the "tool symbol" so that you see the channel settings like in the handbook.

If not already performed you should deselect the "Stereo Button" to get two Mono channels "AN1" and "AN2" IN.
Assumed that you have 2 different Mics and want to operate them in Mono and to perform settings for the Mics individually.
If you have 2 matched Mics and want to perform stereo recordings, in this case you would keep "AN1+2" IN in Stereo.

Click to the "tool symbol" of both channels AN1 and AN2 IN.

If your Mics are condenser Mics you need to enable Phantom Power by pushing "48V".

Then carefully raise the Mic Gain until you get a signal.

In terms of TM FX and routing.

1. ensure you are in submix mode (upper right, blue area)
2. click to i.e. the phones output fader (in bottom row of faders), then you see the submix for phones output

now raise lower the faders of any HW INPUTS and SW PLAYBACK channels, that you want to hear on phones, in this case:

3. Raise the faders of the "AN1 IN" and "AN2 IN" HW inputs, this adds the Mic signals to the submix for your phones HW output. Then you will hear signals coming from both mics in your phones.

In submix mode you can create such submixes for each HW output indivitually.

If you created a submix that you want to use more often, then you can safe it as snapshot and recall it at any time by clicking the snapshot button.

Additionally you should save the routings permanently to disk (Save Snapshot, Save Workspace, Workspace quick select).

RME explains TM FX in nice video tutorials and I wrote a TM FX primer for 1st use.
I am pretty sure both will support you to make the most out of TM FX.
Also the handbook is also very useful.

https://www.tonstudio-forum.de/blog/ind … rnal-equi/

https://www.tonstudio-forum.de/blog/ind … al-Videos/

https://archiv.rme-audio.de/download/bface_e.pdf Handbook EN
https://archiv.rme-audio.de/download/bface_d.pdf Handbook DE