Q: Wireless Bluetooth Headphones Sound Problem

My daughter has an iPod Touch 4th Generation. Bought her some wireless Bluetooth headphones. They worked great for a few weeks now suddenly there's no sound.  The headphones work, I've tried them with my iPhone.  I've removed them from her iPod & re-paired with it, I've rebooted her iPod, I've checked the volume.  Her iPod works with regular headphones, it works with a wireless Bluetooth speaker so I don't think it's an issue with the iPod & it isn't the headphones since they work on my phone.  I've checked the manual (for all it says).  I'm thinking something is muted but there's nothing in the manual that says that's a feature.  Any ideas?