A slight delay can be caused by the time it takes for the signal to reach your earbuds
The wireless audio connection creates a slight delay from when audio is played on the device until the audio reaches your speaker. This delay becomes noticeable when playing audio that is part of a video. This is similar to many Bluetooth® speakers and headsets, which means that you may sometimes experience small latency between the video and sound.
Update your earbud firmware
IMPORTANT: Before updating the earphone firmware using the Melomania app check that your Melomania 1+ are connected correctly.
When correctly connected, Melomania 1+ will show in your device’s Bluetooth settings 'Paired Devices' list, like this. In this case Melomania 1+ L is the primary earphone and Melomania 1+ R is the secondary earphone. They may connect with Melomania 1+ R as the primary earphone and Melomania 1+ L as the secondary earphone, that is fine. You should check that the secondary earphone is powered on, the LED will be flashing white.
If you see the firmware displayed as v0.0.0 the earphones are not connected properly. Before you do anything else follow the advice above to ensure the earphones are properly connected.
You may see the secondary bud appearing as “Headset”, or that there are three devices displayed – this is fine, don’t delete them.