Can maintenance be denied under certain circumstances?

Yes. The law isn't one sided it builds in fairness for the paying spouse too. Maintenance can be denied or stopped if the claimant is guilty of adultery or persistent unchastity, has converted out of Hinduism, has unjustifiably refused to live with their spouse, has remarried, is living separately under a mutual agreement that already settles this, or simply has enough income of their own to not need maintenance.