Q: my mouse light is blinking and mac can not pair, how do fix it?

From what you say I would suggest the batteries are not connecting properly.

First, thoroughly clean all contacts, both inside the mouse and the contact points of the batteries.  Use an alcohol based cleaner, dampen (not wet) a cotton bud for the cleaning.

Check to see if they fit firmly.   If you can shake your mouse and hear things are loose, that will be the batteries.   Check the make.   Apple and Duracell, in that order, are the best batteries.   Some slight undersizing has been reported with other than the two above.

Message was edited by: seventy one