The current version 2.3.0 seems to be incompatible with the new Joomla 3.8.0 Release. I get this message when trying to access Extensions -> Modules:
0 Call to undefined method JModuleHelper::isAdminMultilang()
I found a related issue on the github page of Joomla:
https://github.com/joomla/joomla-cms/issues/18003
Can you please provide a fix?
Oliver