The only way I’m able to upsample to DSD is if I use SDM pack DoP. My source is mostly Tidal Hifi (MQA disabled) into a Topping D90 Standard. When SDM pack is set to “none” and I click stop in HQ Player it switches to PCM mode/Filter/Shaper regardless of SDM default output.
I have no issues upsampling to DSD64-512 within Roon with their DSP engine and native DSD plays fine with Roon as well.
If some other application is keeping the audio device busy, with Thesycon sourced drivers the implication seems to be that DSD output mode starts failing. Maybe they try to do some multi-access/mixing support with PCM and disable DSD for that reason.
Also check that the device is not set as defaut audio output device for the OS!