What should I do, as I vowed to cover the expenses of my mother's umrah if I recovered, and I have recovered, but I have not fulfilled the vow for 12 years due to my mother's own circumstances, as she constantly postpones performing the umrah, and I feel Allah's wrath and lack of blessings in sustenance because of not fulfilling the vow?

Whoever vows obedience to Allah must fulfill it. A vow conditioned upon an event becomes binding if the event occurs. You bear no sin for your mother's delay in traveling for Umrah (definition), as the delay originated from her side, not yours. Fulfilling an absolute vow is not required immediately, according to many scholars. If your mother becomes permanently unable to travel for Umrah, then an expiation for breaking an oath (kaffarat yamin (definition)) becomes incumbent upon you. Making a vow conditioned upon an event is disliked, and the lack of blessing in sustenance may not be due to the vow.