That makes sense! as both these applications Sonic Studio 3 and Nahimic VR rely on the Nahimic audio enhancement framework. As a guess, I would say most embedded premium sound products that are using the Realtek chip would be using this Nahimic sound 3D enhancement framework, MSI and ASUS are two such examples.
I could find precious little re: these fans not working with sound lighting effects. Either people have given up, don't care or maybe not many Riing RGB Plus fan controllers have being sold worldwide . I can't imagine that though, nor that only a few people are having this particular issue, it's easily reproducible much like the issues with Ryzen MBs and Riing controllers.
That said, the ASUS AURA RGB software (which you would have with this motherboard) also has a music lighting mode and behaves as expected with regards sound activated lighting no matter what device is receiving the sound stream. It relies on a LightingSevice.exe service and quite possibly this loads before the the Nahimic framework loads.
In summary, there is just as much chance that the issue is related to Nahimic's framework as it is related to TT Riing Plus software! but my money is on the way the Riing software has been implemented, since the AURA works fine and is not fussed as to who has control of the stream and runs as a service . As an aside, you could try previous iterations of Sonic Studio ie SS2 see if it helps.