After non use for a while, due to firmware updates leaving my old phone unusable, I decided to buy a new phone, A Samsung S8. . . The drone was working before this update.
When I connected the new phone I pulled back or down, and left and right on control sticks, the drone started up ready to fly.

Then the phone came up with "Firmware needs updating", there was a link on the phone screen, so I clicked on it and the controller updated, I ended up with a green light on the
controller.

I reconnect to the aircraft and get a message on the screen I get told the aircraft firmware was out of date.

I have now tried updating the firmware on the aircraft and the update was aborted, stating the firmware I was updating to was either older or the same as that already being used.

Only now when I turn on the controller I get a flashing red light, it won't connect to the aircraft and tells me the signal strength is very weak......
I have tried going into settings on the controller, with DJI Go and when I look at the status it tells me "Linking to Aircraft" I click on this box and I get a pop up that asks " Check Frequency" I click on OK and It does nothing,  I have tried reinstalling firmware on the Controller via USB Cable and it won't link to the DJI Go App......
Yet again DJI's Firmware has turned a functioning drone into a very expensive paperweight,  I have now spent more time trying to sort Firmware problems than I have actually spent flying the drone..... very disappointed with this software and drone.....
I have watched all the tutorials on how to link the drone ( God knows I've done it enough so don't need tutoring). . . none of these tell me to do anything I haven't already tried.

OK  So after much reading of other problem posts and much throwing tantrums, I've managed to get the Gimble Light to remain solid green and the light on the controller is flashing green and silent,   the DGI GO app says the Aircraft isn't connected,  when I look at RC on the app it states "Linking Controller"  but the controller won't link.... when I click the link that asks "Link RC" I click on that and the dialogue box to press the link button on the aircraft doesn't come up, it just loops back to the Link RC dialogue box.  So I now have drone with a solid green light and a controller with a flashing green light.........  If I pull back on the sticks the propellers will start, but I have no link to the DJI Go APP. . . . All Status bars etc read N/A and app states Disconnected.

First mistake :

Using the phone with Internet / data etc. enabled. It is better to Flight Mode the phone to prevent communications other than your Drone. That way - you would never have seen the Update message.

Second mistake :

Not searching out as on Youtube etc. - videos showing how to re-start update to complete. Your update obviously failed to complete fully and any other action other than getting update to restart will fail.

You now have a setup that will take careful study of how to get both RC and AC to update fully.  Suggest spending time on Youtube watching videos how to do it.

If you succeed - then I strongly suggest you Flight Mode your phone next time.