I can't seem to initiate Telemetry with a R7008 receiver. It works and the channels seem to work but when I try to link from my Tx (18mz) I get an error message that says Link fails.
Any suggestion?

If you follow the link procedure and the transmitter says that the link fails, but you still have control over the receiver, something's wrong in the receiver, transmitter, or both, Please make sure the transmitter is set to the correct mode (FASSTest-18 for the R7008).

Activating the appropriate sensors in the transmitter's sensor function (in the Linkage Menu), and then re-linking the receiver will activate the sensor. Receiver battery voltage sensing is automatic, and does not require a separate sensor.

Visited my local Hobby shop that's a Futaba dealer etc. The Step that I either didn't read or didn't understand was not to power the Receiver until AFTER pressing the Tx Link Button but while it was still chiming.
Once that was done it linked right up and displayed the Rx Voltage.

Glad you got it worked out. Enjoy your system!