How can I make my bluetooth earbud volume sync with nexus 6p phone?

When i first got my earbuds, I was able to control the entire volume range from my phone or my earbuds but now for some reason the volume in independent now...i cannot max out my earbuds unless i do it through my phone. Its a hassle. Any help will be appreciated.
P.S i have not touch the development options, independent volume is off