trouble with cigarette adapter...
 

I recently got a CB Radio from a guy at work that he rigged to plug into a cigarette adapter. I have two of those and the one I want it to plug into doesn't give it power at all. the adapter has a snap on cap on it and the other one (the one that does work with the radio) does not have a cap. they both charge stuff because I have a phone charger and fm transmitter that I have plugged in all the time and I have switch the plugs in the past. im just wondering how I can fix this or what is wrong. the one with the cap that doesn't work is on the left and the other is on the right. they both look like they were there to begin with but im not sure because why would one have a cap and the other not? anyway.... if you can help me that'd be cool.

thanks.

its a 2006 Silverado.