What is the cause of the decrease in sexual desire for both husband and wife, specifically the wife's aversion to intercourse and men, despite doctors confirming the husband's good health, and some sheikhs attempting to cast out " عفاريت" (demons)?

Ligature (ar-rabt) is a type of magic that prevents a husband from approaching his family. By Allah's will, it can be cured through patience, abundant obedience to Allah, diligent recitation of dhikr (remembrances), and reading Surat Al-Baqarah in the house every three nights. Sheikh Ibn Baz mentioned an effective remedy: take seven green Sidr leaves, crush them, place them in a container, pour water over them, and then recite Ayat al-Kursi, some Qur'anic surahs, and verses pertaining to magic over the water. Then, drink some of it and bathe with the rest. This, by Allah's will, will remove the ailment. The wife can also do this. One must beware of going to magicians and charlatans. However, there is no harm in seeking treatment from a righteous practitioner of the Sunnah.