Error 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

When accessing Managed Metadata Service the following message is prompt:

"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"

I have done everything that i found on internet on Production and Quality SharePoint Environment and no solution worked for my Production Environment

What i have done:

• Verify the “Managed Metadata Web Service” is "started". Reset several times..
• Recreate the Service Application “Menaged Metadata Web Service”. Set full Permissions on and all others services account in hope it will work..but it didn't happen. It's not permissions issue.
• Publish the same Service Application
• Verify the Service Application Association have Managed Metadata Service is checked.
• Dedicated Application Pool
• Several iisresets

1 - Solution for Quality Environment: Create a new dedicated Application Pool 

1. Go to Central Administration
2. Click Application Management, then Manage Service Applications
3. Select Managed Metadata Service and click Properties
4. Create a new Application Pool

2 - Solution for Production Environment: Reattach Managed Metadata Database

This took me a harder solution.

1. Go to SQL Server detach "Managed Metadata Database". Note: Select "Close Connection" option
2. In Central Administration, Delete "Managed Metadata Service Application"
3. Note: DO NOT Delete data associated with the Service Applications, You are deleting YOUR Database!!!
4. Create a new Managed Metadata Service Application with a different name from the original Database. Note: Select the check-box "Add this service application to the farms default list".
Take the newer database offline and close connections(At the end of this solution, this DB can be deleted)
5. Do an attach of the original database
6. At Central Administration, go to properties of managed Metadata and change the name to the original Database
7. Do an iisreset