Thanks for reaching out! This is interesting - these links do have a different structure. It looks like the second (older) link that you provided is for the exact same file, is that correct? Is the process for getting these shared links any different on your end than it was before?
Thanks for sharing this thread, this is super helpful context. Someone else just submitted this issue on Github for the exact same problem, and it certainly seems like the culprit is the new Dropbox link structure.
We will investigate this on our end and see what we can do to get this resolved, as this shared link is something that a lot of QIIME 2 users do utilize. I'll keep this post queued and provide you with any updates as they become available. Thanks for your patience with this!