I had 2 minis drop out and would not reconnect. 1 was set to my email, the other to my wife's.
Factory reset (even the Hub) still would not connect them, always got to the point of looking for network, then telling me something went wrong, cannot connect or poor wifi connection (being a techie, I knew this was BS) as my Hub and audio connected fine and sitting the minis on my modem was even a waste of time also.
BUT, what did work was creating a new Google acc. with a new email acc. as well then factory reset my Gen2 Hub, my audio and 2 mini's to my network with the new acc. and all worked.
It seems that when you assign individual email acc's you send the hub into meltdown when trying to reconnect stuff back to it.
I was one step away from redesigning them with a hammer before I tried this as a last resort.
Believe me when I say I tried heaps of other stuff trying to connect but rather than write a 100 page book on what did not work, try the above otherwise you too may want to redecorate it's looks with a hammer.
