It’s a bit of a stab in the dark but any chance you have the V1 not V1.2 version of the FC as the Buzzer pads are in a different location for that one.
Main distinguishing difference I can see easily is that the V1.2 has just 745AIO in board writing and V1 has GN745AIO instead.
Take the yellow wire of its pad and touch it to GND (ground) if it buzzes the Vifly buzzer unit works if it doesn’t then it’s either faulty or the built in battery is flat. Using a multimeter check the 5v pad is actually providing 5v, you’ll probably need the LiPo battery connected for this
Ten minutes of 5v power is enough to charge the battery to make it sound.
Thanks for trying to help @DeanoG60 @Steviegeek, @RestlessZombi, @SparkyFPV, @bmsleight.
Fair point. It’s defo the V1.2 board. All the markings (e.g. board orientation arrow) and pad positions match the images of the V1.2.
I tried this - no buzzing.
Confirmed, the pad is giving 5V. I checked at the JST connector that plugs into the buzzer as well, which is also giving 5V.
I’ve had a LiPo plugged in2-3 times for around 10-15 minutes. The onboard battery does warm up and there is a red LED that lights up too, so I assume it’s receiving power correctly.
I’ve emailed Flywoo to see if they can shed some light but they won’t be back from celebrating the New Year until 17th Feb.
From the troubleshooting steps it could still be an issue with the buzzer or the flight controller user/manufacturer setup?
maybe go the cheaper option and just buy another buzzer to try? Worst case it still doesn’t work best case you prove the buzzer was bust and send it back 
Email Vifly as well, they respond quick
A new weekend a new issue to troubleshoot (love this hobby 
). Btw, the buzzer issue is still pending a response from Flywoo and Vifly.
What reasons might the quad be bouncing up and down on the ground when I arm it and leave the throttle at zero? See video link below.
I’ve run through some suggestions I’ve seen online, e.g. I’ve double and triple checked the props and motor direction and order - they’re defo correct.
The board orientation is correct.
I’ve checked for shorts between any of the motors by checking for continuity between the windings and the frame/motor screws - there are none.
The tuning is the default Betaflight 4.4.3, which I thought would be just ok.
It’s worth noting, after doing 3-4 short arms/disarms (as in the video) all four of the motors and even the motor screws and arms feel very warm.
Is this just a tuning thing or is there a deeper issue likely to be at play?
EDIT: sorry gang, I feel like every weekend I’m posting on here for help! I’m very thankful for the help!
The video set to private instead of unlisted mate
Air mode. Top pilots put it on a switch so they can turn it off for perching on ledges without the bounce effect. It’s normal
To test it turn off permanently enable air mode in the configuration tab and try arming and leaving the throttle at zero again
I wouldn’t leave that setting off though as when you go zero throttle while you’re flying you’ll lose stability in the air.
Oops! Try now…
Definitely Air mode
Can watch now (if I click through to youtube anyways). Ummm Is that angle mode? In ACRO I wouldn’t expect that, but the props and motor rotation look fine. If angle then yeah air mode!
Will do it in Acro as well. It’s more apparent on smaller quads because of the lack of weight.
Also sure the sticks are calibrated, and definitely zero reading in the receiver tab on BF? (or 1000 whatever it is!)
I’ve never seen a quad bounce on zero throttle like that. gyro all calibrated, etc, etc.
It’s in acro.
This seems a bit extreme, no? Particularly as I’m going from disarmed and zero throttle, instead of coming in for a landing.
Yep, the end points are setup and reading exactly from 1000 to 2000 on throttle, yaw, pitch and roll.
I’ll give this a try and report back in a few minutes.
Its because its a sub250. You could try and lower your idol throttle value to reduce the effect. Basically because its so light your idol throttle is producing enough thrust to lift the quad off the ground slightly then when it bumps back into the ground air mode kicks in and is causing the bounce effect.
I really don’t think that’d normal even on a smaller quad. Politely disagree with deano on that one. If no throttle has been applied at all after arm.
I have tiny whoops, 2 inch, 3.5 inch and 5 inch.
Is everything tight? I think filtering etc etc. you using rpm filtering? Bidirectional dshot?
Guess we’ll see lol
Well disabling air mode will likely stop it. But that doesn’t fix the problem.
You set your min throttle to 1010? Can’t remember where think in. Receiver tab
Reducing idol throttle is the fix
Turning off permanently enable airmode seems to have made the issue go away but doesn’t necessarily confirm if the previous behaviour is normal.
Similar to gunja99, my Mobula7 doesn’t do this when I arm it or when I land and throttle down to zero.
I have.
According to the Betaflight tip for motor idle (in the screen grab below), this is disregarded if Dynamic Idle is active but I can’t find that setting to check! I can do some trial and error to see if reducing it has any effect.
Screws are tight and bidirectional DDShot is on. I’ve got default filtering as follows:
