That really annoying error that won’t go away about you not being able to make config changes to WSUS as there are some already underway.

Assuming you’ve had this error for a couple of days or more then the fix is below. If you haven’t had this error for a few days then wait longer! Some processes such as changing the languages that you are downloading can take days!!

Fix:

You need to install SQL Management Studio (or SQL Express)
Then connect to the database by using the following servername:

• Server 2012: “\\.\pipe\MICROSOFT##WID\tsql\query”
• Server 2003/2008: “\\.\pipe\MSSQL$MICROSOFT##SSEE\sql\query”

Then run the following SQL query:

UPDATE tbSingletonData
SET ResetStateMachineNeeded = 0

Further Reading:
https://blogs.msdn.microsoft.com/vedvyas/2014/08/19/following-is-the-steps-to-connect-to-these-windows-internal-database-on-windows-2012-machine-this-to-access-the-wap-configuration-from-the-adfs-configuration-database/
https://community.spiceworks.com/topic/737987-wsus-server-cannot-save-configuration-because-the-server-is-still-prcoessing