The group is still active it's just that people play at different times. The PSN SGN community group is by invite only for SGN Members only so you did the right thing by logging on and requesting an invite. Please provide me your character name and @ PSN. Let me know if you also need an invite for Stonewall PS4 Fleet within Star Trek online.
I still play. Fairly frequently. But I play on evenings and in UTC-1, so mostly when you nice people from 'The Colonies' are sound a sleep. If you see me on, though, go ahead chat me up, invite me to your team, flirt or what-not.