Since you can not log in as admin need to deactivate plugins as 90% of time conflicts in theme and plugins or your plugin that is not compatible.
Follow this steps to deactivate your plugins by
creating an empty plugins folder
* Via FTP or your host’s control panel, navigate to the wp-contents folder (directory)
* Via FTP or your host’s control panel, rename the folder “plugins” to “plugins.hold”
* Via FTP or your host’s control panel, create new folder called “plugins”
* Login to your WordPress administration menus
* Via FTP or your host’s control panel, delete the empty “plugins” you previous created
* Via FTP or your host’s control panel, rename “plugins.hold” back to “plugins”
If you can log in then activate one at time see which plugin is causing the problem.