There is something wrong here. Here is the law that applies in PA 18 PaCS 6105
Take a look at para (b)...you can see the offenses that make is illegal for a person to own a firearm. Pornography is not on there (I asked if child porn, since "corruption of minors" is...and thought perhaps that it was related...but it seems not).
BotXXXXX XXXXXne: There is a mistake it seems. The offense you were convicted of is not a bar, under PA law, to firearms ownership.
I would first contact your state Attorney General and get a copy of your criminal record....MAKE SURE ITS ACCURATE. If they have you down for a conviction you did not do, you need to address that.
Then, assuming the record is correct, I go back to the authority that denied your application and request they re-evaluate...do this with a copy of your criminal record and the PA law above in hand.
It seems there is a mistake, either with your record, or with the licensing authority...but it is possible to fix.