This happens when both the earbuds do not pair with each other. 

To solve this, follow the steps: 

• Delete Buds X from Bluetooth pairing history. 
• Reset the earbuds by long pressing the earbuds for 10 seconds.
• Note: Both earbuds need to reset separately. 
• The voice prompt “factory reset successful” should be heard from both the earbuds.
• Keep the earbuds inside the case and then take them out. 
• Place the earbuds inside your ear and tap them 5 times. 
• Wait for 2 seconds, a voice prompt should be heard on both the earbuds indicating that they have been paired. 
• Note: Only 1 Buds X will appear in the Bluetooth list of your device.
• Now pair them by following the pairing process.