Are you exporting journal article references from Endnote? Or do you mean you are direct exporting references from an online database into Endnote? The “Publisher” field isn’t needed for bibliography references concerning journal articles so: 1) the field is omitted from the Endnote reference type and bibliography template; and 2) online database providers omit the field from being downloaded.
If you are exporting Journal article references from your Endnote library, the publisher field is omitted from both the Journal Article reference type and the bibliography template of the output style. So the publisher field will not be exported. You will need to include the field in both the reference type and the bibliography template and provide the publisher data in the Endnote record in order to export the information.
If you are direct exporting the references from the online database into Endnote you might try seeing if the publisher field is included if the references are exported as a text file which then could be imported Into Endnote using an import filter. If the publisher field is available then it’s just a matter of modifying the import filter to include the publisher field in the Endnote record.