The Arcam SA20 amplifier does not recognize the signal from the Volumio Rivo

Hello!
I’ve bought the Volumio Rivo (v3.912), but it doesn’t work when connected via coaxial cable to my Arcam SA20.
When I connect a Raspberry Pi 4 with a Hifiberry DigiPlus card running VolumioOS to the Arcam, it works. If I connect the Rivo to another amplifier, it also works. It’s probably an incompatibility between the two devices, but is there anything else I can try?
Is there any chance it will work when the Volumio 4 for Rivo is released and installed?