I was able to redeem the offer. Spotify Support said that they were aware of the issue (codes were being shared and redeemed fraudulently) and to keep trying. They gave me no timeline, but I was able to redeem within 2-3 days of contacting support. Sorry for those that are still frustrated, but it seems that a resolution is active or rolling out.
Same issue, not working for me and several others. I have been trying for weeks at this point. Google support is of no help either. This is what happens when you don't offer phone support and put your support function out of country. Absolute mess.