@Gromit Thanks! I didn't remember connecting the Link with a USB-A to USB-A cable to the PC when I updated it last time years ago. Oh well, the cable was only $5. Maybe I'll find a use for it sometime.
I connected the Sylphyo cable from the Link's power supply port to the PC and successfully updated the link.
I found that in both cases--the Sylphyo and the Link--the device has to be connected to the PC and powered on first, before running the update program.