I have tried just about all the solutions I can think of.  My sequence of events:
1.  Turn RC on
2.  Turn AC on
3.  Start DJI GoFly 4

Status lights on AC Blink Yellow Fast (Not connected to RC)
RC has red LED

Mobile Always come up showing Spark.  I change to show P4P
Enter AC go to Linking Aircraft.
The LED on AC Blinks Red, No Change on RC.  It does not go Blue

I am using Android.  Thanks for help

Please try to change another working USB cable or recommended mobile to check.