The Managed Metadata Service or Connection is currently not available. The Application Pool or Managed Metadata Web Service may not have been started. Please Contact your Administrator.
After some searching, I will fix the issue: · Backup database of Managed Metadata service · Delete the existing Managed Metadata service application (without deleting the database) · Create a new Managed Metadata service application with new database · Edit the properties of the new Managed Metadata service application, point to the original database (if new managed metadata service is not working) · Iisreset (if needed)