Running Piwik for years, now on version 2.9.1 I believe.
I need to add a few sites. When I go to the website manager page, a red error appears briefly that says:
The method ‘isPluginActivated’ does not exist or is not available in the module ‘\Piwik\Plugins\CoreAdminHome\API’.
and I am unable to add any sites. Any workaround?