I-765 request for more evidence?

My dad has had a work permit for about 13 years and has always gotten it approved. This year, he did all the procedures and sent in the app for the EAD since Feb. 28th and got the notice that it was received a few days later. I know it takes 3 months to process and this past Saturday I got an email stating that they sent a paper in the mail on the 9th of this month that they needed more evidence/info. I checked online at USCIS and it says the same thing. What would they need for "more evidence"? They never asked for any before now, and because of this my dad lost his job. Does this mean they denied it or what?