Phantom 4 Pro not connecting to iPad or Android Phone after firmware update on Phantom 4 Pro. Yellow lights flashing on P4Pro - DJI reports "disconnected. Any suggestions? TIA

Try refreshing the firmware.

What is the error message from your app? Did you try to link your RC with AC first? What is the color of the indicator of your RC? You can change a cable and see if it works. Please notice that you should upgrade the firmware of RC,too.

As Elektra said re-link

That is a pretty easy video to understand.  Thanks for posting it.  I will keep it for future use.

Just activated my new P4P on the weekend. Same problem after firmware update. Solution, also update the Controller firmware.  Appears to be fixed but have not had a chance to fly it yet.