Is it permissible to supplicate for marriage to a specific person when there are circumstances currently preventing this union, and does the non-fulfillment of previous supplications mean that supplication is futile in this matter?

It is permissible to supplicate for a specific person to become a spouse, for supplication is an act of worship, and Allah has commanded us to supplicate to Him and promised to answer. Supplication is never lost; either Allah answers the supplication, or He stores it for the Hereafter, or He averts an evil through it. Among the conditions for supplication are sincerity of intention to Allah and not despairing of the answer; rather, one should be persistent in supplication, for Allah loves those who are persistent in supplication. One must be content with Allah's decree; if He answers, then praise be to Allah, and if He does not answer, then Allah stores good and knows what is best. One must also avoid entertaining ill thoughts about Allah, even if what was supplicated for does not materialize, for Allah's decree is always good for the believer.