If you have the chip then it gives you the option to slot it in when interacting with the console, you do not have to go into your inventory or anything.
What happened with Benny? Did you kill him at the Tops or let him leave and be captured?
More importantly, are you on Xbox?
It is possible to end up losing the platinum chip, thus preventing you from finishing the game's main story line. This will occur if you enter Caesar's legion as an enemy and then slaughter Caesar and his guards, and then choose to let Benny live. Since Caeasar is already dead, the chip will not appear in his inventory, and if Benny escapes, he will disappear from the game and you cannot loot it from his corpse. Paradoxically, even though the chip will not appear in your inventory, you can return to Mr. House and he will act as though you have and have handed over the chip, even upgrading his securitrons and inviting you to return to Caesar's fort and open the secret bunker.
This is, to my knowledge and the Vault's, an xbox only glitch (and again to my knowledge the only way to actually permanently lose the chip)
If this has occurred then I'm sorry but there is no fix there and I can not think of anything, obviously since you'd need to be on xbox for this to occur, console commands are out of the question...