Hi~ 

I'm Spektrum DX6 user.

I was finish the setting Betaflight Receiver menu RSSI value to AUX 8, but that is not working properly. My goggle ODS's RSSI value is not change anymore 99 even the radio has turned off.

My guess is that there are only 6 channels of dx6 radio. It's right? 

You are correct. 6 channels.

Hi Robert, welcome to the forum. RSSI signal is generated through the receiver and sent back to your DX6 so yes, you can see on that the DX6 screen. But to see it on your goggles, you would need an RSSI signal out from your receiver (telemetry) connected to a spare UART on your flight controller so that it can be shown through Betaflight OSD. If it's the AR610 receiver, I don't think it's capable of this .