Restore a SSISDB to another server

I am try to figure out how to recover a SSISDB catalog and database to another new server.I created the key for encryption when I initially create the SSISDB catalog.When I start the step following this Microsoft article:https://msdn.microsoft.com/en-us/library/hh213291%28v=sql.120%29.aspxThe first step is to backup the key using below backup master key to file = 'c:\SSISDBKEY' encryption by password = 'Mypassword'But it failed with Cannot find the symmetric key 'master key', because it does not exist or you do not have permission.I am sysadmin, so I have all permissions, but why it gives this error?Thanks