I've also posted this in another forum.


P4P+ with latest updates works fine. (Controller has android display built in). Very Happy.

Wanted to expand so I bought another P4P controller (no display, with 5.8G capability) for my IPad 9.7 Pro iOS 10.3.2, also running DJI GO 4. It links, the indicator on a/c is green, but controller blinks red/green. I can control gimbal, but got very poor video quality on iPad display. I calibrated the sticks, restored a/c firmware, controller shows latest version. I can also go back and link the a/c to the P4P+ controller, and still works fine. Go to relink with P4P again, blinking red/green controller, and same poor quality video on iPad.

I've read reducing the video quality can help, but don't know where to find those options.

Any Ideas on how to fix this?

Not a solution but I have both controllers and switch between them all the time. I use an iPad Mini 2 which works fine other than some lag in the screen draw sometimes. I use DJI Go 4.1.3 on the iPad and have the latest firmware update. All I do is relink and do a review of the settings to make sure they are where I expect them to be and go. So I'm surprised with a iPad Pro you are having issues but maybe someone else knows something.

I make no changes to the iPad when I link it up. And the only obvious dumb question to ask is that you have the USB Cable from the RC to the iPad correctly and that the cable is good.

I believe the cable is good, I use it for charging, and when connecting to iTunes on my PC.  My biggest concern is not the iPad, but why is the controller blinking red/green while the a/c is green, and linked?  Later today, I hope to first downgrade the firmware on new P4P controller for iPad, then update it thru the a/c SD card slot. I get a short video feed to the iPad, then it gets green, pixalated rather quickly.

I fixed it.  Took awhile, seems like there might be some old techniques in these forums.

I reset the a/c back to default with Assistant 2.
I found that having a SD card in the a/c with the update file on it while linking seemed to work, made it link, but still flashing red/green.  
Then I noticed a status note appear in red, stating the controller needed updating.  That was hard to discover.  I’m sure it didn't see it before.  I went thru the update..
Bingo!

So far iOS works great.

Need time, maybe tomorrow to see if the P4P+ controller still links..
  

Good to hear that you had this resolved. It's because the RC needs to upgrade when it is blinking red/green light. You can also get the reminder on the app's Aircraft Status. Upgrade it and things might get back to normal.
RC's connecting with DJI Assistant 2 can only do a restore factory defaults at present, so upgrade it via APP or SD card.  
Should you have any further questions, please feel free to contact us. We'd glad to help.