If you got a Garmin bundle with the speed and cadence sensors you should be able to pair them with the Edge 830. Most any other sensor for cycling that is Ant+ should also pair with most any Edge.
Perhaps you didn't go through the pairing correctly or it was one of the hiccups that happen every so often with these devices.
A couple weeks ago I'd created another profile for when on my son's trainer. Some how, I buggered up and lost the speed/cadence sensor for my road bike profile and had to re-pair it.
I keep all my sensors paired with my device and not the phone or it's apps.