It's not clear how you calculated a $16,000 credit.
The credit is not the amount you paid back. The credit is the amount calculated on re-figuring your tax liability for the year of the repayment.
It's also not clear when you paid it back, 2019 or 2020, or some in each, and how much. What I'm reading is you only paid back $24,000 in 2020. Depending on your tax rate, that would equate to a tax credit of $2500 to $5500, maybe less. You cannot claim that credit until you file your 2020 tax return, early in 2021.
The credit going on line 73 of form 1040 is the "old way" (prior to 2018). It's now line 13 of Schedule 3, which transfers to line 18d of form 1040.
If you repaid some of it in 2019, the company is wrong; they should have been able to adjust your W-2. Even if they didn't, a repayment, in 2019 (the year the bonus was paid) is handled differently (not a claim of right) than a repayment in 2020.
