Why haven't I received my in-app benefits even though my credits have been deducted?

So I was recently given a 20$ gift card so I redeemed it ( Had $20.06 ) and attempted to buy the 450 Robux Premium for Roblox which is 5$. As it stated how my purchase was set I checked if I had 450 Robux Premium that I bought on my account but I didn't receive anything. So I checked my purchase history and it says that it is pending, however in the app store it says my subscription or " 450 Robux Premium " is active but again I don't have anything. I emailed Roblox twice and I haven't received anything. Also with the pictures showing my credits on the App Store, sometimes it shows that I have $15.06 and sometimes it says I have $0.00. I don't understand what happened nor do I know what to do but this all just ended up to me losing $5 on my credits.