[demodigi]

I don't understand : what's your issue ?

From the Aux point of view (= as a bus receiver), bold yellow means the bus is already assigned/used by another Aux (or Instrument, or Rec_Armed audio, or a side-chain comp input) track.

Ticked white confirms that that bus is assign to that aux track but not any other. Unticked White means free busses.
=> that's what you get, as you have a signal in your input (I don't know why you can't here your reverb, but it's something else, maybe a wet/dry level adjustment ?)

From the send point of view (as an emitter toward a bus), bold yellow means the bus is already assigned to, at least, one receiver (=Aux, or Instrument, or Rec_Armed audio track, or a side-chain comp input), ticked means it is assign to that (those) bus(ses), white means the bus isn't used (at all = not terminated).

If you're not sure, right-click* on your Aux input, or one of your Sends, and choose "Show Only Assignements to reverb bus" (right-clic on "Restore Previously Shown Tracks" to revert back).

* a real right-click (not CTRL+Click)