Parents owe taxes from 2023, even though we already paid off that tax year.

I'm very confused as to why my parents have to pay again for the 2023 tax year. Back in the day, we received the letter that my parents owed the IRS about $750. I helped them pay it off and saved the information, just because I was always taught that it's always good to keep a record. Fast forward to today, and my mother called me that we need to make a payment of $1372.62, because we owed the IRS from the 2023 tax year.

I asked my parents if they mean the 2024 or 2025 tax year, but the letter they got was from the 2023 tax year, and somehow, the new total $1372.62. I went back through my records and checked that I had made the payments for the 2023 tax years. And they need to pay part of the payment they set up with the IRS by this coming Monday.

What can I do to help them out during this time?