I have an immigrant visa but I am not allowed to board the plane.

Take the United States as an example for immigration visas: CR1 for spouses of U.S. citizens within two years of marriage and children under 21 years old, CR2 IR5 for parents of U.S. citizens over 18 years old, IR1 for partners and children after two years of marriage, The children are IR2 F1 U.S. citizen parents apply for unmarried children over 21 years old F3 U.S. citizen parents apply for a family of married children (spouse and children under 21 years old) F4 U.S. citizens apply for a family of siblings over 21 years old and children under 21 years old FX Holder Spouses of green card holders who have been married for two years can bring their children under 21 years old (F2A). Green card holders who apply for newly married spouses can bring their children under 21 years old (F2B). Green card holders who apply for unmarried children over 21 years old can bring their children E1. Experts and professors in science, education and culture. E2. High degree majors. Person E3 Professional talents in short supply, such as chefs EW General workers, mostly in the planting industry C5 investment immigration, 1 million US dollars T5 investment immigration, 500,000 US dollars V92 Spouses and children under 21 years old of those who have been approved for political asylum in the United States V have been waiting to be queued Non-immigrant visas for F2A applicants with a term of more than three years and children under 21 years old A-1 ambassadors, ministers, government ministers, career diplomats or consular officers and their family members A-2 Other foreign government officials or employees and their family members A-3 Attachments, attendants or personal employees of A-1 and A-2 visa holders and their immediate family members B-1; Business inspection personnel B-2; Short-term tourists and short-term family visitors C-1; Foreigners transiting the United States C-2 Foreigners transiting the United States to the United Nations Headquarters C-3: Foreign governments not recognized by the United States or representatives of foreign governments that are not members of the United Nations sent to international organizations and their accompanying persons and family members transiting the United States D-1 Sailors or airmen (accompanying personnel) Those who left the country on the original sea ship or aircraft) D-2 Seafarers or aircraft personnel (those who did not leave the country on the original sea ship or aircraft) E-1 Traders and their spouses and children under the age of 1 from countries that have trade agreements with the United States Unmarried children under 21 years old E-2: Unmarried children under 21 years old of investors from countries with which the United States has a trade agreement and their spouses F-1 Scholars or students F-2 Spouses of scholars or students and unmarried children under 21 years old G-1: Principal permanent representatives and staff of foreign governments accredited to international institutions recognized by the United States and their immediate family members G-2: Other representatives and staff of foreign governments accredited to international agencies recognized by the United States and their immediate family members G-3: Foreign countries who are eligible to obtain visas Government representatives and their immediate family members, but whose government is not recognized by the U.S. government and is not a member of the agency G-4 Officials or employees serving in international agencies and their immediate family members G-5 G-1, G-2, G-3 , Attendants or personal employees of G-4 visa holders and their families H-1a Professional nurses temporarily employed in the United States H-lb Temporarily employed workers in the United States with special talents and expertise H-2a Short-term employment or seasonal agricultural workers H-2b; skilled or unskilled workers engaged in temporary service or labor work H-3; temporary trainees H-4; spouses of H-1, H-2, H-3 visa holders and Unmarried children under 21 years old I; News staff and their spouses and unmarried children under 21 years old J-1; Exchange visiting scholars J-2; Spouses of J-1 visa holders and unmarried children under 21 years old K- 1. Fiancé(e) of a U.S. citizen. K-2. Unmarried children under 21 years old of K-1 visa holders. L-1. Internal transferees of multinational companies. L-2. Spouses of L-1 visa holders and children under 21 years old. Unmarried children under 21 years old M-1; Students studying short-term vocational skills M-2; Spouses of M-1 visa holders and unmarried children under 21 years old O-1; Special talents in science, art, education, business or sports Talented individuals O-2; Persons accompanying O-1 visa holders to the United States O-3; Dependents of O-1 visa holders P-1; Internationally renowned sports players and members of entertainment groups P-2; Performances participating in exchange programs Members of sexual entertainment groups P-3; Performing artists or members of entertainment groups with unique significance P-4; Spouses and unmarried children under the age of 21 of P-1, P-2, P-3 holders Q-1; Participating in international culture Exchange Program Personnel Q-2 Q-1 holder’s spouse and unmarried children under 21 years of age R-1 Pastor of a recognized religious denomination R-2 R-1 holder’s spouse and unmarried children under 21 years of age NATO (1-7) Foreigners and related personnel stationed in the United States under the North Atlantic Treaty