From your description, your foreign tax credit from 5 years ago is from earnings and you would have filled out an f1116 for general category income. Income from dividends is passive category and any thus carryovers can only be used for the same category of income. For TY2020 I'm assuming the 1099-DIV was issued to you in which case if the amount is not greater than $300 (Single) or $600 MFJ) the foreign tax withheld will be automatically end up on form 1040 line 20. The amount in line 20 cannot reduce the tax on line 16 below zero.
