Frank was supposed to lead the VSU Invasion of the ATF in Game Eight. It didn't quite work out that way. While Walt and Mike were picking up his slack, Frank fizzled and died around the middle of the game. You see, as Frank was fond of informing the Czar, he has "a job." Which apparently precluded any sort of outside activity. Including the seven seconds it takes to read and answer your questions. You may have noticed the occasional two-week delays between rounds in Game Eight. Thank Frank.
At the end of the day, despite an incredible average and limitless potential, Frank couldn't be hemmed in by the iron-fisted rule of the Czar. In fact, he couldn't even be hemmed in for 50 rounds. Frank is a loose cannon who plays by his own rules. So he promptly quit answering questions in Round 27. Though he's never officially declared his retirement, Frank and the ATF have definitely parted ways. Sic semper tyrannis!