Already have a DOI number but can't find it My paper was accepted and it was given a DOI, but I can't find yet.
It seems the conference didn't upload the papers for the ACM digital library yet.


Is it normal? 
How long does it take to upload a conference paper to the ACM DL?
ACM normally publishes its conference proceedings just before the conference begins.  The default used to be immediately before the conference begins, but at least some ACM conferences have proceedings available a week in advance.

If you want to double-check (especially if the conference has already happened), you should ask the program committee chair.