What's this fallacy? If masks work, why are states forcing some businesses to stay closed?

I see the claim as just an assertion, without namable fallacy.

See if the asker agrees that masks work to prevent the spread, or merely inhibit it.  It would seem the states' demand for masks is related to their health departments' opinions and their desire to be cautious.  

I am tempted to say this is just a question and not an argument, but as we know, questions can be fallacious (e.g. complex question fallacy ) and questions also contain implied arguments. Assuming the people who ask these questions are not idiots, they are deceiving through ambiguity ( ambiguity fallacy ), that is, they are not being clear in what they mean by "works." We can also say they are using equivocation when using the word "works." Masks and social distancing "work" in that they deter viral spread. The question implies that the claim is that masks and social distancing "work" in that they completely prevent viral spread. Further, I would argue that they are begging the question that everyone is social distancing and using masks. Even if these strategies did completely prevent viral spread, they would only "work" to the extent that people were implementing them.

I would say non of it is 100% and ever bit helps. It is a question that implies an argument that all business should be open or we do not need to wear masks. Maybe hasty generalization or unsupported claim.