CC1125: Constant Rx to measure RSSI

Part Number:CC1125

I'm attempting to use the c1125 to measure the signal strength at a given frequency, to give information similar the the smart rf studio continuous RX test mode where it is constantly measuring the RSSI and printing it to the screen.

However when I read the RSSI registers I'm always getting RSSI1 = 0x33 and RSSI0 = 0x39, which suggests that the RSSI is valid but its not changing meaning that I'm always getting the same dBm value everytime I poll it.

Could anyone suggest a reason why it might not be updating the RSSI? It shouldn't be detecting a sync word as I restart the reciever if I ever detect a match, to the sync that I programmed.

Thanks