Is this a fenix? Which profile are you using to record your activities?
It is a Tactix running the Beta 4.16 software. I am using the Cycling profile when I am recording activities on the bike. I have the ANT+ sensors settings on for the HRM and the Speed/Cadence Sensor. I have had the Beta 4.16 software on the watch since the 18th. I just reviewed all of my files, and the first issue with the cadence showed up on a ride I did on the 22nd. Rides that I did on the 18th and 19th properly show cadence on Garmin Connect.