I see he has the wit to bring them into an anti-magic room. Way to mess with Suspiria. >
Could be as it's not the room, but the man. Perhaps he's one of the Ten, disguised, and is blocking her.
Or possibly he's blocking her, but rather than being one of the Ten, he is an unregistered rogue sorcerer (maybe even the Thin Man himself?), and Suspiria's "ten most powerful" count never thought to take into account all the possible rogues out there.
Or, most likely given the penchant we've seen for illusions so far: Suspiria actually
did shoot a beam o' zap there, but she's being fooled into not seeing it. In such a case, the man is not standing in front of her, either - that's an illusion too. He may never even have existed at all. Perhaps the twins just put him up as a sort of holographic greeter.
No, wait, that's not the most likely option. The most likely option is, as ever, something we haven't even thought of yet.
Edit: 'Nother possibility. Since her hand does seem to be glowing, she may still just be charging up.