It's fantastic to hear that you've now received your cashback from Weight Watchers; thank you for your patience whilst it has progressed.
Generally it can sometimes take up to 3 months for a transaction to become payable although this can vary from merchant to merchant. Purchases based on a contract or policy often take up to 6 months as there may be a validation period.
We have recently introduced a faster payment option for certain merchants so you should see transactions progressing quicker than usual in the future. These are identifiable by a green banner underneath the merchant's logo.