There are two possible explanations for this:
1. Nivå is designed to only emit sound from the Right earbud whenever you're making phone calls or video calls (or using your favourite calling app, like Skype or WhatsApp). When your call has ended, the Left earbud will start working again automatically.
2. If only one earbud is working while you listen to music, that probably means your earphones have fallen out of sync. Don’t worry! We’ve written a handy little guide for you to get them back on track - just click on How do I connect to my NIVÅ?