EV 200 Compass heading variation

[Bob 21]

The compass value is significantly different than the GPS or fluid filled unit. Sometimes it is 60 to 70 degrees different. The only time it is close is when heading south at 180 degrees. After viewing a post from 01/08/2016 I took the boat out to Restart Compass expecting to be able to do 15-20 minute cruise of figure eights. A screen quickly popped up saying Task Complete Maximum Deviation 188 degrees. I ran through Dockside wizard again and still not able to Restart Compass.
What do I need to do to have compass values that are within an expected range? EV 200 purchased 08/2015, software V1.11, Deviation was 20 degrees, now shows ---. Thank you for your help, Bob