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IISSUE SUMMARY: I have and event management plugin installed and I wanted to make an announcement about an upcoming event. When I add the link it picks up that it is one and generates a link in the announcement but when people click on it instead of resolving to the link it brings up a blank page.
not sure what do you mean with "event management plugin". seem that plugin not belongs to jomsocial.
I cant login to site backend and frontend. because the credentials information not valid.
please check your joomla configuration.php and make sure the live site having empty value.
if still cant, please asking more support at that plugin provider.