For the future, I recommend starting a new forum topic. Also, it helps to know whether you’re on a Mac or PC, OS, Ableton version.
If the H9000 is recognized by Ableton, as previously stated, you need to make sure that the channels associated with the I/O of your H9000 are activated in Live’s preferences. If they are not, nothing I’m about to tell you will work, so make sure you have this sorted out.
Then, you have two choices to route audio to your H9000.
1-Directly from the output of the audio track: Where it’s says “Audio To” you must choose “Ext Out” and choose the channels that correspond to the USB I/O of the H9000. Then, you need to create an audio track and set its input to “Ext In” and choose the channels that correspond to the H9000’s USB input. To monitor the audio, you’ll need to record-enable the track or simply choose “In” on the track’s monitor selector.
2-Create an Insert Return tack and assign it the “External Audio Effect” plug-in. Route the I/O of the plug-in to correspond to the I/O of the H9000’s USB channels. From the audio track you want to process, send it signal from the corresponding Send knob.
In my sessions, I like to route H9000’s USB IN 1-2 to the inputs of FX Chain 1. Then, I take FX Chain 1 output and connect it to USB 1-2 Out. I do the same for FX Chain 2 (USB 3-4), FX Chain 3 (USB 5-6), FX Chain 4 (7-8). In each Fx Chain I have four of my favorite effects in parallel that I can mute or unmute at will.
Other ideas: You could put 4 algorithms in parallel in two FX Chains, for a total of 8 algorithms, and route stereo pairs to each algorithm. In Live you can have 8 Eventide returns in stereo. Or route 16 mono channels to 16 mono algorithms and 16 returns. Your choice.