HyperFlux V2 no LED / no charging with Basilisk V3 Pro 35K on desktop (works on laptop)

Hi Razer Support,
I have a Razer HyperFlux V2 mouse mat and Basilisk V3 Pro 35K that I cannot get working together on my desktop PC.
Problem:
Both the mat and mouse appear in Synapse 4.
The mouse with the correct HyperFlux V2 puck is detected, but the mat never lights up (no LED at all, no charging indication).
The mouse does not charge wirelessly on the mat.
What works:
The exact same HyperFlux V2 + Basilisk V3 Pro 35K setup works perfectly on my laptop (LED lights up, charges normally).
Desktop specs:
Motherboard: ASUS TUF Gaming Z790-Plus WiFi (latest BIOS version 1836)
Connected directly to rear USB-C and USB 3.2 ports
Troubleshooting already done:
Clean reinstall of Synapse 4
Correct HyperFlux V2 puck installed and clicked in place
Mouse powered ON
All Windows USB power management settings disabled (Selective Suspend, per-device power saving)
Multiple rear motherboard ports tested
BIOS tweaks: ErP Ready set to Disabled / Enabled (all variants tested)
Latest BIOS update performed
Full power cycles, CMOS clear, etc.
Could you please help diagnose this issue? I have attached the HyperFlux V2 serial number: L12526V19200522