The Bluetooth feature on your Apple computer provides a wireless connection for your wireless keyboard and mouse, but you need to replace the battery periodically to ensure that the peripheral device continues working as expected. If your computer cannot detect your wireless mouse after you replace the battery, you may simply need to restart the mouse. If the problem persists, you can resolve common connection issues by unpairing the device and the computer and then pairing them again.
Turn off your Bluetooth-enabled mouse. Click the Apple icon on the desktop, then click "Restart" to restart the computer. Wait for the computer to restart and return to the desktop, then power on the wireless mouse. The monitor will display a mouse icon and "Connected" when the computer detects the wireless mouse.
Click "System Preferences" on the desktop's dock and select "Bluetooth." Click the name of the mouse in the Bluetooth window. Click the "Settings" icon in the bottom-left corner of the window, and select "Disconnect." Wait for the indicator light below the mouse icon to turn red, which signifies that the mouse is disconnected from the computer. Plug a wired mouse into your computer's USB port, then click the "Settings" icon. Click "Connect" to reestablish the connection between the wireless mouse and the computer.
Click "System Preferences" on the desktop dock using a wired mouse, and click "Bluetooth" in the System Preferences window. Click the wireless mouse's name, and click "-" to remove the wireless mouse configuration from your computer. Click "Yes" to confirm that you want to delete the configuration settings. Click the left arrow button in the top-left corner of the window, and click "Mouse." Turn on your wireless mouse, and click "Set Up Bluetooth Mouse" in the Mouse window. Click "Pair" once the computer detects the mouse in the Bluetooth Setup Wizard.