If you're on xbox, try changing your gamertag profile through the game, and then logging back in. - Load up your character and get to orbit like normal, then press Start/Menu > Settings > Log Out > Switch Profile - You should get the title screen, then a dash screen should appear to let you pick a gamertag. Select the same one, and you should be brought back to Destiny at the character select screen. - Now pick a character, and then wait a little bit once you get to orbit and see if any of the achievements pop.