So update. Not sure if this work for those that saw this post. I didn't complete the first mission on legendary with my first character(a hunter class) and went ahead and started the missions on ky 2nd character( a warlock). It marked the invitation mission as completed on my title, but I had to actually go in and get it done with my hunter and not another character. In order to replay any of the specific missions I had to go through the fireteam finder and make a temporary lobby to just summon myself back to that mission since I was playing it solo anyway. Once I completed that mission I only had to go to the alter on kemplar and claim my chest armor. Hope this helps those other guardians out there.