There are a few common things that can cause the Apollo Twin to not be recognized by the computer. Here's what to check if you're getting the 'No Devices Found' message in the UAD Meter:

Check Thunderbolt Cable Orientation

When connecting Apollo Twin to the computer always check the orientation of the Thunderbolt cable. The Thunderbolt logo must be face up on the Thunderbolt cable when plugged into both the Apollo Twin and the computer - if the Thunderbolt logo is not face up then the cable is inserted upside-down, which can be done fairly easily. 

Note: On iMac computers, the Thunderbolt logo on the Thunderbolt cable should face left (when looking at the back of the iMac).

Check Computer Compatibility

Apollo Twin cannot be used by connecting it to a Mini DisplayPort connector. Although Thunderbolt and Mini DisplayPort devices have the same physical connector, the underlying communication protocol used by these devices is different and the Apollo Twin will not be recognized when connected to a Mini DisplayPort.

The type of device port can be determined by the icon next to the port. Thunderbolt ports have a "lightning bolt" icon, while Mini DisplayPort ports have a "display" icon. The difference between these ports and icons is shown in the illustration below.

Still having trouble? Check out the Apollo Twin Basic Troubleshooting article.