The American Opportunity Education Credit is available to be claimed 4 times per eligible student. This count includes the number of times you claimed the Hope Education Credit.
For example: If you claimed the Hope Education Credit on your 2015 tax return and then claimed the American Opportunity Credit on your 2016, 2017, and 2018 tax returns, you will not be eligible to claim the American Opportunity Credit on your 2019 tax return. Your other education credit/deduction options would be the Lifetime Learning Credit. If you are filing a return prior to 2018, you can also use the Tuition and Fees Deduction (expired in 2018).
Please note that you are unable to claim more than one education credit for the same student in the same year.