Have you tried the solutions discussed multiple times above
Option 1
- Open Manager desktop
- Open a Manager desktop link in your normal browser (which is the same as opening http://127.0.0.1:55667 )
- Minimise the initial Manager desktop window and do not use it until you want to quit Manager
Option 2
- Upgrade your Mac operating system.
Option 3
- Continue to use an old versions of your Mac operation system and an old version of Manager