After you file

I filed on March 12. The income tax service I paid to file my taxes, forgot to include a w-2 form. It has been almost a month now, and my refund says is being processed and that it is delayed in the IRS webpage. My concern is, I’ve read that if it was rejected I have to file again, and the deadline is April 18th. How long does it take for the IRS to process refunds when a w-2 is missing? 
How can I know if my refund was approved? The person said my refund was approved the same day he filed my taxes (I don’t believe it).