Follow the directions below to reset your Apollo x16 hardware:
1. Power off Apollo x16 and computer.
2. Disconnect any cables connected to Apollo x16 except the power cable. (this includes disconnecting the Thunderbolt cable). If there are any monitor speakers or headphones connected to Apollo x16, make sure that they are either disconnected or powered off before continuing.
3. While Apollo x16 is powered off, press the Meter button and the Monitor knob on the right side of the display (see picture below for reference).
4. Keeping the buttons pressed down, turn on the power switch to Apollo x16 - hold down the knob/button combo for approximately 10 seconds until all LEDs on the front of Apollo x16 remain lit. Once all LEDs on the front panel of Apollo x16 are lit you can release the two buttons and shut Apollo x16 down once more - note that the LEDs will stay lit until the unit is shut down.
5. Reconnect all cabling and power up the system like normal.