We just received a brand new P4 RTK multispectral drone, and I'm seeing some weird issues.  
First, I tried using the DJI Go 4 app on both my iPhone and iPad to control the drone, but got an error, "The current device cannot use DJI Go 4, please check the relevant manual and download the correct app to use."  I checked the manual and it says to use DJI Go 4.

Second, I was able to run DJI Pilot but the sattus shows "Aircraft Disconnected".  Checking the details I get "Unknown error (code: 102), cannot take off, please contact DJI support".  Then "Aircaft Encoder Error", and "Solution: Please restart aircraft, if the problem persists, contact DJI Support".  I've tried restarting the aircraft and that doesn't work.  There's also no video signal from the drone displayed in the app.  The rear indicator lights on the drone are slow-blinking red after connecting to the controller.  The status light on the controller is solid-green.

I've also noticed that in the DJI Pilot app, under About, it's not able to read the Flight Controller Serial Number.  I also can't format the internal storage of the drone or the MicroSD card.  Under the controller settings I am able to see feedback from the Controller Calibration when moving the sticks, so there is some communication happening.

I've tried updating the controller firmware, resetting the drone to factory defaults, downgrading the drone firmware, updating the drone firmware, and re-pairing the controller and drone.

I tried contacting DJI support, but they said that RTK has a different support line, and that they'd contact me in 48-hours, but I was wondering if anyone out there might have an idea of what might be wrong.

Thanks.

You can only use DJI GSpro on Ipad, or UGCS on android.

LV_Forestry Posted at 5-24 12:34
You can only use DJI GSpro on Ipad, or UGCS on android.

Thank you.  That worked.

You're welcome

I have now the same exact issue. Except that we used the Phantom 4 RTK already for over a year with success. Then just one day, the errors appeared.

Indeed, it seems that DJI GSpro works. But it shouldn't be the only working app. Why is that? You still need DJI Go for manual flights.

Did you ever solve the actual issue?

kuarvikozza Posted at 6-2 04:41
I have now the same exact issue. Except that we used the Phantom 4 RTK already for over a year with success. Then just one day, the errors appeared.

Indeed, it seems that DJI GSpro works. But it shouldn't be the only working app. Why is that? You still need DJI Go for manual flights.

Why do you want to use DJI Go for manual flight? GSPro does the trick.

It's like that for all end-of-life products. With DJI you should know that you are not buying a product with an unlimited lifespan. The functionalities of the app are voluntarily altered at the end of their support.

It will just be honest to announce it when buying the product, it will allow us to make a more effective business plan. Rather than finding yourself one day in front of a customer with defective equipment.