The housing office I applied through told me I didn't qualify to receive assistance, and I don't know why. What could have made me ineligible?

Any housing office that provides a HUD program is legally required to explain to you why you did not qualify. Due to the high demand of affordable housing, and comparatively low supply, it is possible that you did qualify, but were not among the applicants that were placed on the waiting list. For example, 20,000+ people may apply to a waiting list opening that is placing 1,000 applicants on that waiting list.