What do you mean?
You’ve got an Ant+ USB dongle, plugged it in & it’s not working?
If so, you should just plug it in, it’ll go through the normal ‘new USB device recognised’ gubbins and then it should work.
Are you sure the USB port works? Are you sure the dongle works? Have you tried a different USB port? Turned it off & on again?
If yes to all of those, then I’m not sure why it wouldn’t work. The one I use for Zwift was just a cheap Amazon job that I plugged in & it worked straightaway & has continued to work for the last 6+ years, so that’s unfortunately the limit of my knowledge.