Even when a DOI has been assigned to an object in OJS it is not automatically known to the registration agency and the corresponding URL at http://dx.doi.org/ will not yet be resolved. You’ll have to register the DOI with one of the DOI registration agencies first. At the time of writing, OJS supports registration with Crossref, mEDRA and DataCite out-of-the-box. You pay a membership fee to register your journal with one of these agencies and sometimes a small fee per DOI registered. Some agencies are more suitable for certain types of journals and their prices vary. It is also possible that an organization you already belong to provides membership in one of these agencies.
The next section describes ways to register your DOIs with mEDRA and DataCite. For instructions on how to register with Crossref, see the Crossref | OJS Manual.