Why does it need to populate? It is designed to provide a simple drag-n-drop for a binary file.
Why would it connect as a UART?
Probably crashed the driver stack at this point. Remove connection and reboot.
AV software or policies blocking USB Storage Devices? Performance or Remote Diagnostic Tools (Intel / DELL)?
Connected via a Hub or Docking Station?
Try using a different cable, rated for High Speed
Have only one application open the ST-LINK at a time.
It should really need updating out of the box
Download the Firmware Update application separately
https://www.st.com/en/development-tools/stsw-link007.html
Click to get it into upgrade mode, it should enter its DFU mode and reenumerate.
Current version of Cube Programmer is v2.6.0, just click the "Get Software" button, don't fiddle with the version option
https://www.st.com/en/development-tools/stm32cubeprog.html
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