I haven't had any problem with it except when I forgot to connect my phone to my wireless network. Works great. Is the Mi Box not showing up in the list of available devices?

You should give this app a try instead: https://play.google.com/store/apps/details?id=fr.bouyguestelecom.remote

It's a total ripoff of the official Android TV Remote app, and part of the UI is in French, but somehow it works much better and is much more reliable than the official app.

Mine would never connect..showed mibox3 but no dice....fast forward to last week and I factory reset the box and the app worked after i set it up

You will probably need to factory reset. For unknown reasons, the MiBox is prone to a wide range of wifi/networking issues. I had to reset 3 times before I could get casting to work. I also highly recommend NOT updating after factory reset at least until you try all your apps first. If it all works, never update .

It wasn't working for me until I changed my rotuer's security mode from wp2 to wep, then I was able to do the pairing, and after that, I activated back the wp2 mode in my router. Some other places suggest to turn off WWM from your router.