Does anyone else have this problem - sometimes when I choose to engage the Borg Red Alert the ships are there and I can engage tme, but sometimes once I get there, there are no more borg ships. Also, the text of the objective of "exit to Sector Space" changes to red with an "X" (I guess meaning objective failed)...but it shows that I failed the objective before I have the chance of exiting.
If you can't engage the borg that means the Alert is over - someone else already did it. It just hasn't faded from the zone yet.
STO is about my Liberated Borg Federation Captain with his Breen 1st Officer, Jem'Hadar Tactical Officer, Liberated Borg Engineering Officer, Android Ops Officer, Photonic Science Officer, Gorn Science Officer, and Reman Medical Officer jumping into their Jem'Hadar Carrier and flying off to do missions for the new Romulan Empire. But for some players allowing a T5 Connie to be used breaks the canon in the game.
It's a known bug. Try subscribing to the Redalert channel. People will sometiems report in that channel if a particular one is bugged. Also they'll let you know when they see one that ISN'T bugged too.