Edit: Realized after posting this the last time OP was here, hope it's been corrected by now for you.
For others like me doing google searches this issue this is for you lol
I had this issue as well, when the DAC was first setup the remote worked perfectly then all the sudden it didn't. Tried different batteries and it didn't seem to be working.
Thanks to
@Harmonie for the life hack tried to see if the IR was working still on the remote and was able to see the pulsating red light on the remote with my phone's camera.
TLDR--Started pressing all the buttons individually (A, B, C, mute, power, etc.) on the remote and ended the sequence by pressing C like 3 times turned the DAC off with the knob then tried to power on with the remote and it actually worked. Remote seems to be working for now.
Idk if there is a bug but on the same Firmware as
@AudioStudies there is no other Firmware listed on SMSL's site so not sure if there is even another version.
Hope that this "fix" works for you as it did for me but love the DAC so far, only other issue is that when my PC goes to sleep for a few hours the DAC seems to loose it's signal/handshake and have to power cycle it to get Windows to see it again.
Good luck