Try this solution
The volume of your earbuds and your device may be operating independently
If you’re not getting high enough volume on your Melomania earbuds with your Android device, please make sure the volume is high on both devices:
To increase the volume on your Melomania earphones:
1
Check the playback volume is turned up on your device, then press and hold the Right earbud button whilst the music is playing.
2
You should hear the music getting louder, release your finger once you are happy with the volume.
Reset any EQ settings that may be configured
This includes any settings in the Melomania App, for the device itself and the app used to play audio. EQ settings may alter the sound of your Melomania 1+ earbuds.
The EQ in the Melomania app can be adjusted by selecting the 'Equaliser' page along the bottom bar and choosing one of the available pre-sets.
Perform a factory reset of your earbuds
1 Place both headphones in the charging case.
2 Press and hold both buttons until the earphone LED's flash white.
3 Wait for the LED on each Melomania 1+ to blink blue three times.
4 The LED will then go back to the “breathing” white display.
5 At this point, you can release the buttons as the reset procedure is complete.
6 The earphones will no longer remember any of the devices that have previously paired with them.
7 When removing either 'Melomania 1+ L' or 'Melomania 1+ R' after a reset, you will hear the voice prompt saying “Waiting to Pair”.