Here is the explanation I got on the Ampario surveys.
"Thank you for emailing us here at TrialPay. I am sorry for any inconvenience or confusion you may have encountered when attempting to complete Ampario Surveys offer through the TrialPay checkout process to receive WGT - Credits for free.
Please note that the partner offer inventory is constantly changing and not all offers previously available will be eligible for completion to receive WGT - Credits. If you are still unable to access a particular offer after waiting 24 hours, please select an alternate offer that suits your needs to receive your free product.
If you have any additional questions or concerns please do not hesitate to email.
Regards,
Kelly
TrialPay Customer Support"
So basically what they are saying is tough luck I guess!