He was age 17 for most of 2020. Did he really have a lot of income in 2020?  As was noted a LONG time ago, you need to determine if he qualifies as a dependent.  Assuming he was a full-time student for at least parts of 5 months, that mean did he pay for over 1/2 of his own support?

As a side note, if he turned age 17 in 2019, then the parents received the $500 credit based on their 2018 tax return, not 2019.