The I-821D is filed concurrently with the I-765. This is a requirement. If you got approved for the I-821D (DACA) this means you must have filed for the I-765 as well. It is possible not to get employment authorization in the event you did not prove "economic necessity." However you should have received a decision in the mail along with your approval for the I-821D. Consult a competent immigration attorney who is a member of AILA (American Immigration Lawyer's Association) who can assist you by checking with USCIS further and determine your next steps.
The answer provided here is general in nature and does not take into account other factors that may need to be reviewed for a more precise answer. You should consult with an immigration attorney before taking any action. The answer here is not intended to create an attorney-client relationship.
Did you file it at the same time? If you do not get it you need to contact USCIS.
Please be advised my answers to questions does not constitute legal advise and you should not rely on it, due to the fact that we have never met, I have not been aprised of the facts in you case nor have I reviewed any documents.