microcell not working for iPhone

@Avedis53 - hmmm, I'll have to go back and see what I wrote. It's my understanding that WiFi Assist is there to help you maintain a connection when cellular is weak or non-existent and there is a stronger WiFi signal. It does chew up battery because of the constant "searching" for a signal and yes, your data plan will take a hit as well because even tho the connection is WiFi, it sill goes against your plan.

Actually you have it reversed, the wi-fi assist helps maintain connection by using cellular data when your wi-fi connection is weak. That's why it chews up battery and data, and why I have it disconnected

@brtman64 - yep. Thanks for the clarification. 

Wi-Fi Assist helps your iPhone switch to cellular data with your carrier when your local Wi-Fi is too weak to offer fast enough loading speeds.

THANK YOU!!  THAT WORKED!!  I was using an iPhone SE and couldn't get it to pick up my microcell, just posted my own question and then saw this reply and it worked... thanks again for posting the help!!

@pdz1971 - disabling WiFi Assist?

So, my iphone 7 and my wife's iphone 5 quit connecting to our Microcell a few days ago.  They had been connecting routinely for years before that.  I called AT&T Wireless Tech Support, TWICE, and they had no idea what to do.  I realized what the problem is when I read this post.
However, what I don't understand is WHY, all of a sudden, our phones want to choose the cell tower signal over the Microcell signal, when we STILL only get 1 bar most of the time.
This makes no sense.  Is it something in the Microcell firmware that was reset recently?  (One of the techs said that AT&T is phasing out the Microcell, since most iphones have WiFi Calling ability, which I do not want to use!)

@JiffSee18 - AT&T will be discontinuing the MicroCell service once they begin to transition away from their 3G network. They have discontinued sales by AT&T as of the end of 2017 because the MicroCell has reached its EOL.

WiFi-C is what AT&T and us recommend now. If you don't want to switch to WiFi-C, then your only other options will be to purchase a cellular booster or switch carriers once the MicroCell service goes away.

We would need more information as to how you have your MicroCell setup, who your ISP is and type of service, and probably most importantly, the model of MicroCell and what the light pattern looks like on the MicroCell. It could be that your MicroCell has died of old age, the ac adapter is failing or has failed, or your ISP is doing something to the ports.

@OttoPylot - Thank you for your detailed reply.
Our MicroCell DOES work just fine.  It's just that our iPhones now CHOOSE the cell tower signal over the MicroCell signal MOST of the time.  The only time the phones choose the MicroCell is if the cell tower signal drops off.  When we first got the MicroCell (maybe 7 years ago), our cell tower signal was typically either one bar or none.  Now, we have 1 to 4 bars.  However, it was only a week ago that the phones STARTED choosing the cell tower most of the time.  THAT seems like it must have been a change in the MicroCell firmware.  Nothing else explains it, does it?