I have now read your first post more carefully. I see you didn't reinstall the patch before upgrading. So it makes me think that the fcc mod you installed two months ago was the old version.As you can see I did all the ABove suggestions
As you can See in my post I did all the above Suggestions.
The FCC .exe App Kept on replying that 0100 was the Highest Dji-RC firmware to Patch
Also the Lowest Dji Assitant will allow is Firmware .0400