Going through the initial setup of Phanthom 4. Everything worked as expected.
However, after I upgraded the COntroller firmware, the controller no longer connects to the Phanthom 4 aircraft.
How do I make this work?

Try relinking.

Hello and good day Ravikumar. I am sorry to know that you are having issues with the connection of your DJI Phantom 4 to your Remote Controller. I understand that you have upgraded the firmware of the remote controller. May I know if you have also updated the firmware of the DJI Phantom 4? For reference I will provide you a link where you can find the most recent firmware of the DJI Phantom 4. Please give us an update on the situation. Thank you.

https://www.dji.com/phantom-4/in ... te_search#downloads

DJI Stephen Posted at 12-17 13:05
Hello and good day Ravikumar. I am sorry to know that you are having issues with the connection of your DJI Phantom 4 to your Remote Controller. I understand that you have upgraded the firmware of the remote controller. May I know if you have also updated the firmware of the DJI Phantom 4? For reference I will provide you a link where you can find the most recent firmware of the DJI Phantom 4. Please give us an update on the situation. Thank you.

https://www.dji.com/phantom-4/info?site=brandsite&from=insite_search#downloads

The first step was upgrading the Controller. The App did say that I may have to update the Phantom 4 firmware next. However, I couldn't get to that step, since the Upgraded Controller SW is not connecting to the Aircraft!

What should I do?

I did power down the aircraft and controller in sequence and powered up controller and aircraft in sequence several times. The aircraft wouldn't still connect to the controller.

Ravikumar Posted at 12-17 13:54
I did power down the aircraft and controller in sequence and powered up controller and aircraft in sequence several times. The aircraft wouldn't still connect to the controller.

Just re-link the controller in the APP or do it manually it is not difficult.

Good idea to read the manual beginning to end.

OK, I read the manual. Manually relinked the Controller to Phantom 4. The indicator lights are green on both the controller an don the Aircraft.
However, my DJI Go 4 App still says that the Aircraft is disconnected. In fact, the display on my app doesn't seem to have anything to do w/ my controller at all.
Wondering if it has to do w/ my App being on Android 7.0 device (Samsung Galaxy Tab4
I would like this working so that I can upgrade the Phantom 4 firmware as well and get flying!

Turns out, this is an Android issue. This is how I overcame it.

First the description of the problem:
I followed the instructions and powered up the RC, then the AC, and then started the APP on my Android Tablet (Samsumg Galaxy Tab4). The app never connected to the RC. However, I could see by the green lights on the RC and the AC, that they had successful linked.
I finally found a blog that suggested that I should
1. Start the Tablet (while connected with USB cable to the RC)
2. Stop all applications
3. Start the DJO Go 4 APP
4. Select Phantom 4 for the AC and notice that the APP displays "Disconnected".
5. Start the RC and notice a banner asking you want to make DJI as the default APP for USB. Select "OK"
6. Notice that the APP now displays "Connected" and offers "Enter Device"
7. Start the AC and let it link with the RC
8. Notice the "Enter Device" change to "Go Fly"

Now you are all set to go flying.

This works repeatedly well.

Once in a while, the banner asking you to select DJI APP as the default for USB, would disappear. In that case, you have to make sure that all other apps are stopped, and start all over. If, even after that the banner disappears, you may have to swipe the top margin down to expose USB options and select "none" as the required mode. This will redisplay the banner asking if you want to make DJI the default APP for USB. Select "OK".

I was able to get the system to work acceptably in this manner. This isn't the most reliable method, but it does the job.