The app shows disconnected but the RC is definitely connected to the bird.  I have gimbal control.   I'm using a Samsung Galaxy S4 w/ Android 5.0.1 and in the app is shows poor connection however I'm in my backyard about 20 feet from the house with nothing else behind me (no other homes).  I've tried two different USB cables so I do not think the cable is an issue.  I also had problems getting to go to camera mode but finally resolved that issue by launching the app first before I turned anything else on.
Is there anyone who can help me with suggestions on how to fix this?

I had the same problem after upgrading to 1.3.2.  I have iPhone 6+.  Could control gimbal, fly, and take pictures, but no FPV on the iPhone.  App said "disconnected".  This was after everything seemingly going right with the upgrade and getting "success" in the .txt files.  I tried 4 different cables including 2 Apple-brand lightning cables.  Deleted and re-installed app, etc.  It is now in the black hole of DJI repair - they say 7-8 weeks.  
I had zero problems with previous upgrades including with my P2V.

You may have to re link your controller.

Turn on your controller
Turn on your Phantom 3
Start the Go app
Open the controller settings menu
Scroll to the bottom and press "Linking RC"
Press the link button on the side of the Phantom 3 with a paper clip or the likes of
Wait a few secs and all shoul be good

Hope this helps... It solved my problem.

pstrats Posted at 2015-8-23 06:22
You may have to re link your controller.

Turn on your controller

or, put your device in airplane mode and if ios device, change the lightning cable to oem. if android, get a good quality cable.
you are advised to do what i have just mentioned in the manual.

Same issue here at times, sometimes with video, sometimes without video.  Phone in airplane mode, reboot the phone, boot up rc, boot up p3, run the app.  Warms up, looks good all around. May fly for 10 minutes before failing, or may not fail at all.  Always maintains control, sometimes maintains video, but shows disconnected.  On a recent flight, I rebooted the phone again, unplugged, plugged the cable in, started the app, and it still wouldn't connect (bird still flying-hovering where I left it).  It still didn't connect and I had no video this time, so I brought it down, shut everything down, and started all over again.  No more incidents during that project, even after shutdown and changing battery.  Galaxy 5 Android 5.  Distance to bird, 50-100 feet.

Just out of curiosity, what was the tempature outside when you were operating the P3? Was it hot?  More specifically did the tablet get hot?

The reason I ask is, I know when mine was getting hot before I had upgraded the pilot software I used to have overheating problems that just made the video freeze. Since the app upgrade when operating in a hot temperature it just loses signal and the only way to fix it is to shut down the app and reopen while in flight. So I went back to using my cold pack fix and now the problem is solved.

Follow this link

-Dog

pstrats Posted at 2015-8-23 06:22
You may have to re link your controller.

Turn on your controller

Thank you but I actually took a step backwards.  Before I saw your post I decided to uninstall and then reinstall the app.  Now I can't get past the how to connect screen to get into camera mode.   Any suggestions?

pstrats Posted at 2015-8-23 06:22
You may have to re link your controller.

Turn on your controller

Big THANK YOU.  This took care of it.  I registered the bird and now it wants me to register it again so once I figure that part out I should be flying!

Robertbaron001 Posted at 2015-8-25 13:22
Big THANK YOU.  This took care of it.  I registered the bird and now it wants me to register it ag ...

Just to be clear, what worked for you?  re-linking the RC to the phantom, or re-enstalling the app?
I'm having the same problem.  It works 50% of the time.  Its not an over heating problem, it was -5C when I was tying to fly today.
If the solution is as simple as re-linking, I'll give that a try.