Is what befell me—the failure to complete an engagement after it has happened repeatedly—a result of being afflicted by an earthly gaze (nadhrah ardiya), as one of the healers mentioned? And what is it that I can do, or wherein am I falling short, especially since I am lax in performing ruqyah? What do you advise me to do?

You must continue supplicating and entreating Allah to facilitate marriage. The delay in marriage is not necessarily due to magic; it could be for a wisdom known only to Allah, or it could be due to an unusual cause. Therefore, one must be patient and consistently perform ruqyah as prescribed by Sharia, while being careful not to go to charlatans and sorcerers.