I've not had this problem, but it's interesting that they're both bard class characters. Are they performing? (Volo would be whistling and Alfira playing her lute.) I ask because I think I did once get the "not now" from Alfira at the party when Alfira & Volo had joined in with my bard performing, and hadn't quite returned to their normal animation when I spoke to her.

(I've never got Volo's song at the party, I just assumed this hadn't been implemented yet but perhaps I have a bug.)

"You may call it 'nonsense' if you like, but I've heard nonsense, compared with which that would be as sensible as a dictionary!"