It’s been over 20 days almost a month and I still haven’t received my refund nor a letter in the mail stating why.

 When will you get your refund,
https://ttlc.intuit.com/community/refund-status/help/when-will-i-get-my-irs-tax-refund/01/25589

Was your return Accepted? First double check your efile status here
https://turbotax.intuit.com/tax-tools/efile-status-lookup/

When you efile you get back 2 emails. The first email only confirms the transmission. The second email says if the IRS (or state) Accepted or Rejected your efile.

Then only the IRS can tell you. IRS Where's my refund https://www.irs.gov/refunds/
Make sure you are using the refund amount from your actual federal tax return and not the combined amount Turbo Tax showed you at the end. That was for federal and state combined.

When you log into your account you should also see the status and if it was Accepted or Rejected, Started, Printed, Ready to Mail, etc.  what does it say?