Thanks for letting us know about the missing reward.
It could be that you were temporarily disconnected when you launched the app - please just launch it again.
If credits are not added please send us a "screenshot" that clearly shows the app (or the email you received after completion, if there was one).
iPhone / iPad - Press the Home button and the Power on/off button at the same time
Android devices - Press the Volume Down and Power button at the same time
to make a screenshot
Please note that you are only eligible for payout if you were not a user of this app prior to downloading the app through Fyber.