I have a DJI Mavic Pro that, up until recently, operated without issue.
My questions are as follows:
(please see my previous steps for attempted solutions below these questions)
- what would cause (and is there any significance in) my led indicator light next to the linking button not functioning?
- why won't the AC be recognized by DJI Assistant 2 for Mac?
- can I upgrade/downgrade the AC firmware without having connection to it via DJI GO 4 or DJI Assistant 2 for Mac?  
- what other solutions are there for binding the RC and AC or solving the "Aircraft Disconnected" message on DJI GO 4?


Background story...
A few weeks ago, at an event, (following several successful flights on the same day at the same location) I lifted the drone into the air and noticed my gimbal was erratically moving in all directions.  I immediately grounded the drone and powered it down in order to inspect it and the gimbal.  Once I verified that the gimbal was not visibly damaged or "in a bind", I attempted to launch again.  However, my display had the dreaded red banner in the upper left corner reading "Aircraft Disconnected".  The drone would not respond to remote control commands and there was no video feed coming through the DJI GO 4 Application on my iPhone 6s Plus.

Since then, I have attempted the following with no luck:
- attempted to connect the AC, via USB cable, to DJI Assistant 2 on my MacBook Pro (downloaded fresh from DJI Download Center https://www.dji.com/downloads/softwares/assistant-dji-2) in order to up or downgrade the AC's firmware.
* the RC will connect to DJI Assistant 2 but the AC will not
- downgraded RC firmware to V01.04.0100
- upgraded RC firmware to V01.04.0500
- binding the RC with the AC through DJI GO 4
*I have tried this using the original iPhone 6s Plus that was being used at the time of the issue, as well as with a new iPhone Xs Max and an iPad Pro (all running iOS 12.3.1)
- fully charged the AC & RC battery
- fully drained and recharged AC & RC battery
- connected the RC to apple device(s) with the provided microUSB to iPhone cable and relaunched DJI GO 4
- connected the RC to apple device(s) with Apple USB cable and bottom-center USB port on the RC

So far, none of these steps have resulted in any positive progress.  I am still stuck with the flashing yellow LED on the tail end of the AC and solid red LED's on the front 2 wings of the AC along with the red banner error reading "Aircraft Disconnected" on DJI GO 4.

I've scoured these forums for help but have come up empty.  Any help or thoughts are appreciated!

Hi ChrisLCrawford, sorry for the troubles on linking the RC, upon your description, the RC works fine, please check the firmware of the aircraft to see if its firmware matches the firmware of RC.
Did you try to link them via buttons? Press C1 Button, C2 Button and Record Button at the same time, when the RC makes the following 'D-DD', press the Shutter Button, the RC will beep quickly and display 'Binding' on the screen, then press the link button to start linking.
The DJI Assistant version in MAC is v1.2.4, was the driver installed successfully? Any chance to try a Windows computer to see if the drone can be recognized?