On my 6300, if I select RCA TX 1, it does not work. No keying on my accesories (relay) I have tested every posible combination and nothing. No other programs running on pc. It is like this since new version with different settings for each band (v2.5.1)
As Jim already commented, this menu is a NEW item under "Settings" and it is called "TX Band settings..." on the 6700, 6500 and 6600 (not sure on the 6300) you click ON the "RCA TX1" if your running Amp keying on that port on the bands you want to use the Amp/relay on.