Your USB-to-DMX adapter - whether it's an Open DMX or a DMX USB Pro - uses a chip made by a company called FTDI, and Windows needs FTDI's driver to talk to it. On a new or freshly reinstalled PC, that driver often isn't there yet. One driver covers both adapter types.
How to fix it:
- Download the FTDI driver here: https://ftdichip.com/drivers/d2xx-drivers/
On that FTDI page, find the D2XX Direct Drivers section and click the link there labelled "Click here to download the Windows 10…". That's the one-click installer - it installs everything both adapters need.
- Run the installer you just downloaded and click through it. Say Yes if Windows asks for permission.
- Restart your computer. The FTDI driver only takes full effect after a restart.
- When Windows is back up, plug your DMX adapter back in and wait a few seconds for Windows to set it up.
- Open SDC's Hardware Test again and press Re-scan. It should now show green - ready to send.