If you used an online tax preparer, that may be the reason your stimulus check is delayed.
Here's why. The direct deposited payments that are bouncing from temporary or alternative bank accounts used to receive the first round of stimulus payments which the companies now closed. They include Refund Transfer services used with tax prep software and reloadable pre-paid debit cards.
According to Steven Mnuchin, the Treasury Secretary, he tweeted on December 29th "These payments may begin to arrive in some accounts by direct deposit as early as tonight and will continue into next week."
In order for the refund transfer to work, the preparer creates a temporary bank account to receive the refund, takes their cut, then passes on the rest to the filer and closes the account. The IRS used the closed bank account on file, leaving some funds in limbo.