Just purchased the new speed and cadence sensor from Garmin. Tried to pair it with my Edge 800 - separately as I should. I can get the speed sensor to work, but not the cadence. I have removed the speed sensor from the room, but still nothing. Is there a way to test the cadence sensor to see it it is working? Or do I just have a bad unit? Can they even be paired with the 800? I am ready to send it back.

you should be able to pair it. Is it definitely powered up? Is it magnet-less?

I have mine on my shoe, but since I only use it indoors, I have never paired it with my 800. One of these days...

In the USA, Garmin has wonderful phone support and has always been very helpful when I actually talk with them. The email support is sometimes helpful, but more often not, so I almost always call them.

Though frequently there is a long wait time, their system lets you request a call back and they will call you back. They'll help you get your sensor paired if it is compatible with the 800.

I don't know about the edge 800, but my 500 and some of the other devices I've paired sensors too don't exactly tell you when and what they are paired to if you miss the one time 2 second notice they flash when it happens. So if you have not tried it out, go ride and see.

Are you moving when you try? I have trouble pairing things up until I'm actually on the bike and moving and then it all just appears. No amount of shaking my shoe or spinning my wheel seems to be enough, I have to be fully engaged. This is for both my head unit, a Wahoo Bolt, and any of the various computer based apps. It does get frustrating sometimes as both Zwift and Sufferfest want all things paired before you can get started, even just to look. I guess you can bypass, but then I can't get either to pair without fully exiting.

I finally got it working, thanks. I am using it on an indoors bike and disabled the gps. That was a mistake. It is working fine now

Referring to Garmin,
I'm pretty sure the new sensors don't turn on until the wheels/cranks are rotating, at which a tiny green led lights up to indicate "on".
Certainly this is the case with my 1030 units sensors.