Mount the E90 on the aircraft and power them on. Using toothpicks or paperclip shaped into a U hold both reset buttons in for 15 seconds and then release. Cycle power off and then back on. The reset buttons are recessed and right next to the SD card slot.
The "4 slow tones followed by 3 quick ones" is an IMU failure code. If you did a compass calibration after the update with the camera mounted and no gimbal lock, one suspect would be a damaged ribbon.
Mount the E90 on the aircraft and power them on. Using toothpicks or paperclip shaped into a U hold both reset buttons in for 15 seconds and then release. Cycle power off and then back on. The reset buttons are recessed and right next to the SD card slot.