I checked on my side with Raspberry Pi 4B + Tone2 + Volumio, Tone2 is detected.
Volumio version: https://updates.volumio.org/pi/volumio/3.757/Volumio-3.757-2024-09-17-pi.zip
Please double check the connection to Tone2 is correct.
Tone2 only supports SPDIF IN, so the connection you want is like this ?
Raspberry Pi → Allo DigiOne —SPDIF–> Tone2
If so, you can check the Tone user manual to setup input source to SPDIF IN.