This error occurs when you attempt to activate a plugin from the Plugins page in your WordPress admin.
The plugin installation did not complete, either because it is still running in the background, encountered an error that interrupted it, or for some other reason is corrupted
Delete and reinstall the plugin:
- Go to Plugins
- Locate the plugin and clickthe Delete link below it
- Wait for it to completely delete, then navigate to your theme's plugins page to reinstall the plugin. If the plugin was installed from the Add New page, search and install again but ensure the plugin you are installing is approved for the current version of WordPress and has been updated in the last 6 months.
If issues persist or you are unable to delete the plugin this way, you may do it via FTP. See Cannot Install Plugin, Folder Already Exists