The rules for being able to claim a dependent have not changed for the 2020 tax return. If everything was fine up until the time that you entered the Social Security number, then you should double-check the number that was entered. If it was entered incorrectly then it may not have been recognized as a valid number.
To review the rules for claiming a dependent, take a look at the following TurboTax article: Who can I claim as my dependent?
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