It sounds like you're doing exactly what you're supposed to, but I'll go over what I would do and see if anything works.
You've already verified that your iFly's connect to the Stratus 3 WiFi. And there's no ForeFlight involved here.
Go to Menu>Setup>ADS/B (may have Waiting in () ) OR click on the ADSB Status instrument. Either way you should end up with this:
If it looks exactly like the box above, you're somehow not connected to the Stratus, or the Open ADSB switch isn't on. You should have green check marks next to each (or most ) item in the list.
If it doesn't say "Stratus III" like above, or you don't have the green checks, click "Options". You'll get this:
If it doesn't say "Stratus III", click on "Change Selected Device" and select Stratus III from the list.
If you don't have the green checks, click on "Reset / Reconnect".
As I recall, it does take a minute or so for my Stratus 3i to get itself all set up and ready to do whatever it is it does.
I realize you probably already have done all this, but it's all I know to do.