[xucheng]

It’s quite common for a DOI to be assigned to a paper after it’s accepted during camera ready. However, the DOI won’t work until the conference or journal version is published on the official website (ACM in this case). The version you’re viewing now is simply a preprint directly from the authors.

[feraloink]

Exactly! It says this as one of the 3 reasons for DOIs not found on the error page:

>The DOI has not been activated yet.