Tax Refund Says Approved Should Be Deposited Today

My tax refund says it's approved and should be on its way today. I first checked my bank account this morning to find that it has yet to be deposited, I then checked the, Where's My Refund? tool on the IRS website its still marked as approved, but it has not been sent yet. I have called the hotline and all it gives me is the automated service to track my refund even though I would like to speak to a live representative and not a machine. I'm curious as to what is possibly causing the delay? Thank you.