I've also gone into the services and made sure that MC21 is automatic startup
You altered this yourself, and this will
break MC. It should be set to
Manual.
MC starts as a user-space application, not a service, and then the application itself launches the service as is needed. If you have the JRiver Media Center 21 Service set to load automatically at startup, it loads before any user is logged in as the system user, and then MC itself (when it tries to launch) it is unable to load its own service (and probably crashes the whole thing).
Set the Service back to
Manual in Services.msc and then simply set the startup option normally through the MC Options dialog. It sounds like you have it messed up so you might need to:
1. Toggle MC's Startup option back off
2. Close MC fully (including the notification area Library Server icon if running)
3. Re-open MC and toggle the option back on
That should get you sorted.