It could be me, but there doesn’t seem to be an Issues tab on the OJS GitHub repository. I’ve found a coding error.
OJS-Stable-3_0_0
File: ojs/plugins/generic/googlescholar/GoogleScholarPlugin.inc.php
Line 99:
if ($language = $article->getLanguage()) $templateMgr->addHeader('googleScholarLanguage', '<meta name="citation_language" content="' . htmlspecialchars($language()) . '"/>');
Should be:
if ($language = $article->getLanguage()) $templateMgr->addHeader('googleScholarLanguage', '<meta name="citation_language" content="' . htmlspecialchars($language) . '"/>');
The second instance of $language should not have parentheses after it.