Firstly, we know that it's frustrating when you complete an offer and it doesn't pay. If you don't get paid for a successfully completed offer, contact the offerwall. All offerwalls control their own content and offers, and only the offerwalls can trigger a claim for their offers.
Most of the offerwalls have a support system built right into their offerwall. Others have a contact form, including:
MinuteStaff: https://www.minutestaff.com/contact_us.php
Tap Research: https://www.tapresearch.com/contact
Adscend Media: https://adscendmedia.com/contact
Thank you.