On a Muḥrim Who Is Prevented from Entering Makkah

Answer—and Allah grants success: If it becomes impossible for him to reach Makkah and he finds no way to do so, he must send a sacrificial animal (hady) to be slaughtered in Minā during the Days of Sacrifice if he is in iḥrām for Hajj, then he releases from iḥrām after it is slaughtered. If he is in iḥrām for ʿUmrah, it is to be slaughtered in Makkah.
The proof is His saying: “Then if you are prevented—[offer] whatever can be obtained of sacrificial animals; and do not shave your heads until the sacrificial animal reaches its place of sacrifice.” [al-Baqarah: 196]. If the muḥṣar (the one prevented) does not find a sacrificial animal nor its price, then he fasts three days and thereafter releases from iḥrām after completing them, and he must fast seven more days after the three. If he is unable to fast, al-Manṣūr Billāh, peace be upon him, said: it is permissible for him to release from iḥrām, and the hady remains a debt upon him. Imām al-Mutawakkil ʿalā Allāh strengthened this. This is mentioned in the marginalia of Sharḥ al-Azhār.1
Then the muḥṣar must make up that for which he was prevented from completing.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.1