Hello, I've been having this same issue for the past few weeks now too. Last night my band rehearsed and we all just used Qmix to mix our in-ears but then when it came time to power down I opened up UC Surface on my iPad 5th Gen to safely shut down. The app would see the mixer, then I press to connect, then I see the control light go blue and then...nothing and the mixer on the scan list would disappear.
So would I set the Dynamic IP from the mixer itself? Or my router, thanks for your answer!