Per IRS Publication 970 Tax Benefits for Education, page 12:

You can't claim the American opportunity credit for 2021 if any of the following apply:

• Your filing status is married filing separately.
• You are claimed as a dependent on another person's tax return, such as your parent's return.
• Your modified adjusted gross income (MAGI) is $90,000 or more ($180,000 or more if married filing jointly).
• You (or your spouse) were a nonresident alien for any part of 2021 and the nonresident alien didn't elect to be treated as a resident alien for tax purposes.
• You weren’t issued an SSN (or ITIN) by the due date of your 2021 return (including extensions).

Note that any link in the information above is updated each year automatically and will take you to the most recent version of the webpage or document at the time it is accessed.