Hi Sparky 1955,
I use my iPad mini 3 to fly my P e advanced, P 4 and my Mavic Pro Plat. Have you first closed all your running apps on your iPad mini 4? Then I turn on my controller, then the P 4, I wait for like 30 seconds or so then open the DJI GO 4 app, when I do it in this sequence all my birds connect perfectly. I've never had the problem your describing, in sure one of the guys here can help if you have already tried what I suggested, these guys on here are very knowledgeable and great guys to.
Good luck...
SteveP55