The person who received the first-time homebuyer credit was you, not the new owner. You are responsible for repaying the credit. If you transferred the title and stopped using the house as your principal residence, you must repay the remaining amount of the credit on your tax return the year that you did that.
Why did you mention 2018? Did you mean 2008, which would have been the year that you purchased the house and received the credit?
If you stop using the house as your main residence for any reason, you have to file form 5405 to close out the credit. You either repay the entire remaining credit in a lump sum, or you make a partial repayment, or you pay nothing, depending on the circumstances.
If you moved out before 2024, you were supposed to report that fact in the year you moved out. If you moved out in 2024, you should indicate that fact, and the program should ask you some questions to complete the form 5405 to calculation how much more you owe.
Or, since 2024 is the final year of repayments, you can just say you still live in the house (even if you don't) and make the final payment this year.