just cross checked before suggesting to RME a manual update, beause it appeared strange to me, that no such information is in the handbook, that it would be mandatory to use an USB3 port for flashing.
So I plugged USB2 cable (which is usually connected to my ADI-2 Pro) to the UFX+:
- Windows Device manager clearly shows "RME UFX+ USB 2.0"
- TM FX starts up
- fut_mfusb3.exe flashes the device through USB2 without any issue.
Could it be, that your UFX+ was set to another "Interface mode" like e.g. "USB3" ?
With "Auto" everything works here like a charm, check on the UFX+ display:
"Button Setup: Options->Interface Mode: Auto"
Would be interesting if you could check that again.
My Setup: Win 10 Pro 21H1, Sonnet Allegro Pro USB3.0 PCIe, 4x Fresco Logic 1100 Chipset using Microsoft Win10 driver.
X10SRi-F, E5-1650v4, Win10Pro21H2, Cub10Pro, UFX+, XTC, 12Mic, ADI-2 Pro FS R BE, RayDAT