I wrote a complaint to FTX regarding the same issue yesterday. The answer to the complaint was that Apple was to blame and that I would have to contact Apple.
Taking their suggestion, I had an extensive conversation with the Apple CS team. The answer to my issue according to Apple was that the situation in my particular case is due to an update in the Narcos Cartel Wars game. This update caused a situation where the Narcos Cartel Wars games terms no longer met Apple's requirements.
The unfortunate thing here is that I had already initiated two tasks on the Offer Wall while the icon for it still was showing in the app and was available for Apple/iOS users.
One task is already fulfilled, and the other one was about to be fulfilled. Both tasks were signed up for during the period where the offers on the Offer Wall granted double rewards for fulfilling the tasks.
When speaking to the Apple CS team they made it very clear that this is not their responsibility, and that there would a small matter to FTX to compensate their players for the time they have spent on mentioned tasks. In fact it won't cost FTX anything, considering that FTX would have had to compensate me (and other players) anyway unless this conflict of interest between Apple and FTX had occurred. Considering the time spent on those tasks, it would be extremely unreasonable of FTX to ignore this issue.
I expect FTX to compensate me for my efforts shortly, as I should not have been a victim to a legal disagreement between Apple and FTX, nor should anybody else.