MARQ aviator can not join the flyGarmin ?
https://fly.garmin.com/fly-garmin/devices/add-device
Have you tried? it’s included in the images of compatible watches.
It does upload to fly.garmin.com... a bit more details are needed to find your issue
MARQ aviator seems did not include in the flyGarmin device database.
It is if you look at the screenshot I provided. You do have to scroll down as the devices are arranged alphabetically.
It works for me (always did), so have you simply tried it?