To fix this issue, please try the steps below;

1. Remove the maximum volume limit on your phone. Go to Settings > Sounds & Haptics > Headphone Safety and turn off Reduce Loud Sounds.

2. Make sure the charging case has enough power and reset the earbuds by following the steps below:

   * Open the charging case and take out the earbuds.

   * Press and hold the touch areas of both earbuds simultaneously for 10 seconds.

3. Clear all the pairing records on your phone and re-pair your earbuds. Turn the volume down one notch on your phone. Then turn up the volume of both your phone and earbuds with the music/video to the maximum. 

4. Use a Q-tip with a bit of rubbing alcohol to gently clean the metal mesh filter under the rubber ear tips.

5. Check whether the soundcore app has turned on the maximum volume limit: Safe Volume--> limit High Volume