Is VoucherCloud reliable???

A Couple of days back, vouchercloud had 75£ voucher reward for purchase from AO for 250£ & above. I purchased nintendo for 259£ and it was tracked.

I checked the status last week and now it does not show any rewards. I raised a query with customer support. They suggested me to logout and login back which didnt help.

My main concern is, how reliable vouchercloud is? What is they rejected the voucher for some reason or if my rewards goes missing like it did now? Any inputs will be helpful please.

Thank you