This is the 6th logitech H390 I've purchased. Never had an issue before. Bought in November as a backup and just now opened it. Disappointed that the right ear doesn't work at all. Can't find any troubleshooting on the internet. All other logitech headphones (same model) continue to work just fine so I'm positive it is NOT my USB port. Sad it's too late to get a replacement. Should have opened and tested it when it first came. $40 bucks down the drain.
Update: Contacted Logitech and told them the situation. They are sending me a replacement!