The I/O utility is the best option for routing audio to/from the H9000. Can you share a screenshot of your Audio MIDI setup page that shows the inputs/outputs of your aggregate device? It’s important to note the input/output numbers to route the audio properly.

On the H9000, make sure the output of the FX Chain is assigned to a USB output. Loading the Reverb Busses default session will have audio routed on the 16 USB channels.

You can also load the oscillator algorithm in your FX Chain and this will output a constant tone to make it easier to troubleshoot which tracks the audio is being output from the H9000.