Here was my problem:

I crashed my Phantom 3 Pro drone into some trees a year ago, and let it sit until last week. I finally got around to buying the parts to fix the aircraft. After hardware replacement, I updated the firmware on the aircraft. I plugged the tablet that I had always used (a Nexus G9) into the controller and was prompted that the app must be updated; I obliged. After updating the app I noted the following symptoms:

1) Tablet would charge but would not prompt me that it was in debugging mode (developer options were turned on, debugging mode on and MTP mode selected in the android settings) Note: I plugged my tablet into my laptop and the tablet recognized debugging mode. Only my RC would not recognize debugging mode
2) With tablet plugged in, app would indicate "camera" for the Inspire. Note: I do not own an Inspire nor have I ever
3) With tablet plugged in, app would indicate "How to Connect" for P3P. Note: I have had my P3P registered for almost two years
4) Iphone 6S plus I have would not do anything when plugged in

What I tried to fix it (these were all recommendations that I found on this forum, but none of them worked):

1) Tried to update firmware via memory stick (yes, I know that after v1.3.2 you have to use the app, but I tried it anyway to elminate that)
2) Replaced both cables: new micro-USB for my andriod tablet and new litening cable for my iPhone
3) Deleted and reloaded app on both devices
4) Rebooted devices
5) Attempted different sequences of turning on aircraft, RC, and device
6) Try to manually relink RC to aircraft without app

What I did to fix it:

I had read some threads that the USB ports were faulty on a lot of RCs. I bought the HDMI USB card because I couldn't find the standard USB card for sale, and I was getting impatient. I installed the HDMI card into the RC and my tablet still wouldn't connect. When I plugged in my iPhone, the device was recoginized, "Camera" was indicated for the P3P, and I was prompted that my RC needed a firmware update. After updating the firmware on the RC, I tried my android, and it was finally recongnized.

Now I'm flying again.

I've read a lot of threads where users are pontificating their ideas about what be wrong, and I've noted that a LOT of people have experienced my EXACT problem with no viable solution ever offered--leaving many users frustrated and on the verge of giving up. I am not saying that this is going to fix your problem if in ANY way it is different than mine, but hopefully someone experiencing the EXACT problem I have explain will find use in this thread(I know you're out there). If you aren't experience what I have explained, you may have other issues.

It seems that DJI has some configuration management issues, but I cannot blame them as they must support a multitude of peripheral devices for their aircraft. The unfortunate piece of this puzzle is that I needed to use an apple device to fix a problem with the android side of their firmware.

Good luck all!

Here was my problem:

I crashed my Phantom 3 Pro drone into some trees a year ago, and let it sit until last week. I finally got around to buying the parts to fix the aircraft. After hardware replacement, I updated the firmware on the aircraft. I plugged the tablet that I had always used (a Nexus G9) into the controller and was prompted that the app must be updated; I obliged. After updating the app I noted the following symptoms:

1) Tablet would charge but would not prompt me that it was in debugging mode (developer options were turned on, debugging mode on and MTP mode selected in the android settings) Note: I plugged my tablet into my laptop and the tablet recognized debugging mode. Only my RC would not recognize debugging mode
2) With tablet plugged in, app would indicate "camera" for the Inspire. Note: I do not own an Inspire nor have I ever
3) With tablet plugged in, app would indicate "How to Connect" for P3P. Note: I have had my P3P registered for almost two years
4) Iphone 6S plus I have would not do anything when plugged in

What I tried to fix it (these were all recommendations that I found on this forum, but none of them worked):

1) Tried to update firmware via memory stick (yes, I know that after v1.3.2 you have to use the app, but I tried it anyway to elminate that)
2) Replaced both cables: new micro-USB for my andriod tablet and new litening cable for my iPhone
3) Deleted and reloaded app on both devices
4) Rebooted devices
5) Attempted different sequences of turning on aircraft, RC, and device
6) Try to manually relink RC to aircraft without app

What I did to fix it:

I had read some threads that the USB ports were faulty on a lot of RCs. I bought the HDMI USB card because I couldn't find the standard USB card for sale, and I was getting impatient. I installed the HDMI card into the RC and my tablet still wouldn't connect. When I plugged in my iPhone, the device was recoginized, "Camera" was indicated for the P3P, and I was prompted that my RC needed a firmware update. After updating the firmware on the RC, I tried my android, and it was finally recongnized.

Now I'm flying again.

I've read a lot of threads where users are pontificating their ideas about what be wrong, and I've noted that a LOT of people have experienced my EXACT problem with no viable solution ever offered--leaving many users frustrated and on the verge of giving up. I am not saying that this is going to fix your problem if in ANY way it is different than mine, but hopefully someone experiencing the EXACT problem I have explain will find use in this thread(I know you're out there). If you aren't experience what I have explained, you may have other issues.

It seems that DJI has some configuration management issues, but I cannot blame them as they must support a multitude of peripheral devices for their aircraft. The unfortunate piece of this puzzle is that I needed to use an apple device to fix a problem with the android side of their firmware.

Good luck all!