After finishing the SA mission chain I can visit Mark’s room, he speaks to me, is very polite but also very shy. He’s invisible and can’t be interacted with. I can do and turn in his side mission but I cannot shop.
Ran the length of the mission area and came back, still invisible.
Ported to Agartha and back, invisible.
Met up with someone who claimed they could see him, invisible.
Logged out and back in, invisible.