Digital keys/codes can run out because they are almost always produced in batches instead of on demand. You make more when you run out of the first batch (or ideally when you’re close to running out so there’s no gap). Remember how they ran out of codes for Endwalker because I guess they didn’t foresee the demand? We had to wait for SE to generate more. For promotions like the Dew one it’s probably even worse because as part of their agreement they were probably only allotted a set amount of codes for the whole event, or they simply ran out too close to the end of the event to obtain more even if SE would have handed them over.

Either way, considering the event ended over two weeks ago, this thread seems unnecessary.