Problem connecting a speed/cadence sensor to my vivoactiv 4S

Did you "wake up" the sensors before trying to connect?

Spin them a couple times to wake up. They don't stay connected when not using the bike.

Yes, I did. In fact, I was pedaling on the bike. Here are screen shots of my Garmin.

1. Yes, that's right: the sensors are paired to watch and NOT phone nor Connect.

2. No, these are NOT Garmin sensors. They are sensors coming by default with the spinning bike. The Wahoo app recognizes them as "JFICCycle".

3. The speed and cadence icons are blinking.

4. The status of the sensor is "searching" all the time when I'm not pedaling.

What I tried: power off bluetooth of my phone, delete the pairing in my wahoo app., power on/off the watch, delete and repair on my watch. Still, no connection. 

I tried to find those sensors online, no luck searching.

Maybe try searching the spin bike maker and see if they define the sensors..
I don't have any info on what brands the Watch Cycling app will or will not work.
I have 2 sets of Garmin Speed 2 and Cadence 2 sensors that come up as BLE.

Maybe a phone call to Garmim Support will be easier and faster.

And yes as long as you are in the Watch/settings/sensors you will see them searching.

Sorry, can't help. Good Luck.

I already contact Garmin Support (by email). They told me that my watch can only connect to ANT+ sensors (which I think is false) and since my sensor is on bluetooth low energy (BLE), it can not connect to the watch. 

I will try to get info from matrix about their sensors.

Thanks a lot for your time.

ANT+ only? Their own Speed and Cadence sensor is both ANT+ and BLE.

From their sensor page:
"ANT+® connectivity and BLUETOOTH® Low Energy technology let you sync to Garmin Connect and other training apps, compatible devices and fitness equipment for better data when you ride indoors and outdoors. "

I suppose it may be possible that the Cycling app may not work with BLE, but why would they do that? I don't know enough about the app to guess how it works. Maybe someone else here will chime in.

Android phones are going to be moving away from ANT, if not already. If Garmin's apps only support ANT then they are falling behind.

That's what I told her. I'm very disapointed of Garmin Support. They don't know the answer and instead of telling me they don't know, they are answering whatever comes into their head 

Today the wife told me she wants to look for a spin-bike for her use because she does not like having to readjust everything when she uses mine.

I see that most have BLE built in, a few have ANT+ so now I'm worried about her not being able to have her rides become activities and go to Connect via her VA4s. Never would have thought this was a problem with today's technology.

The VA4(S) does not support power sensors, but you can always record indoor bicycling activities with heart rate from the watch or chest band. Speed/cadence sensor is a bonus if you can log it too, but not really important. The speed/distance of a stationary bike is rather meaningless data.