Destiny 2 You Must Restart The Application Using Blizzard

I downloaded the game yesterday on pc and am unable to play as every time i boot up the game, i am met with the message you must restart the application using blizzard's battle. net app in order to play destiny 2. Not sure what the problem is for so many folks. Bought deluxe pc edition from greenmangaming. com last night for $20 off. Registered at greenman, got a key, entered it to get a bungie key, registered at bungie after linking my battle. net account, entered that key.