Can't use my Fairbuds, no sound and disconnect quickly

Hello,
I have a Faibuds XL for few months and I have a problem I can’t solve alone now.
First of all, I did the same tests with my friend’s phone and same result. Secondly this is the second time it happen, Don’t now how I fixed it, it worked one time for few hours and then comeback to the problem.
I can start the headset, I see the white light flashing but no entrance sound.
When I click on the button to change the ambiance mode, no sound.
Then I can connect to my Fairphone 3+ but when I play music, there’s no sound.
And after few seconds it disconnect from the bluetooth.
It did’nt fall, I’m pretty sure it’s not damaged.
I tried to do the reset factory with 5 seconds to the right on the joystick. The headset is up to date.
Can you help me on this please?