What do you mean by "starting the vCenter"? From the rest of your post it seems you are trying to connect the Firefox browser on your Mac to your vCenter Server?
Tried the various URLs here? Log In to vCenter Server by Using the vSphere Client
Has this ever worked? Have you tried a different browser?
Hey, hope you are doing fine?
Can you attach some screenshots please?
Is the vCenter service started?
Have you added a security exception on firefox?