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Which Bluetooth mouse?

Is the mouse listed in your Bluetooth menu, under devices? Try clicking the connect "button" in the mouse device sub-menu.
Or, do you see the mouse in your Bluetooth pref pane?
Have you tried making the mouse "discoverable", either by turning mouse power off, or pressing a connect button (depending on the device)

Bluetooth 4.0 did not appear in a MacBook Pro until the 2012 models.
 
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