Not only can co-ops take as long as they please to review your application and schedule your interview, they can also turn down any buyer and not disclose the reason. Officially these rejections should take place only for financial reasons, but then why do they request things like background on your family and education, and why are financially qualified candidates sometimes summarily rejected?
While high-profile lawsuits and stepped-up enforcement of fair housing laws have many boards mindful of their responsibilities especially towards protected groups (race, creed, age, marital status, sexual orientation, gender identity, disability, etc.), some discriminatory bias still lurks, unfortunately.