Magic Mouse will not work.

Hello marshmokhtari,

It sounds like your Magic Mouse won't turn on, so you are not able to pair it with your computer. I found an article with some steps to help with issues with the Magic Mouse. I recommend starting with these steps from the article:

Make sure the wireless mouse and keyboard are turned on.

Mouse

• Slide the On/Off switch on the bottom of your mouse to turn it on. Note: If the battery compartment cover is not installed properly the On/Off switch may not function correctly or may be difficult to operate. Remove the battery compartment cover and carefully reinstall it.
• When your mouse is on and paired, and the batteries are charged, the indicator light glows steadily.
• If your mouse isn’t paired with a Mac, the indicator light will blink, indicating your mouse is in discovery modeand ready to pair.
• If the indicator light doesn't illuminate, check to make sure you have two good batteries and that they'reinstalled correctly.

You can find the full article here:

Troubleshooting wireless mouse and keyboard issues

http://support.apple.com/kb/TS3048

The batteries also need to be facing the same direction as seen in the image below:

The article with steps to replace the batteries can be found here:

Apple Wireless Keyboard, Mouse, and Trackpad: How to install batteries

http://support.apple.com/kb/HT3903

Thank you for posting in the Apple Support Communities.

Best,

Sheila M.

This is going to sound super ghetto, and I also realize it's 3 years later but I'm positive more people who own the non-recharge-able magic mouse have this issue.

The ➕ side of all batteries has a nub. This nub is too small on some batteries, to fit properly into the magic mouse battery slots. So I took some tinfoil and folded it up to add a millimeter or two to the inside of the ➕ terminals inside the magic mouse. I just place them in the holes and then add the batteries, and everything fits, works fine.

I've had this magic mouse since 2010. Serves me well and it's over half a decade later. Easy fix that works, if you don't mind using two square inches of tinfoil inside. Cheers.

It's not the nub that is too small; it's because you are maybe not be using the recommended batteries. Eneloop, Duracell and Energiser are the best. Other batteries do tend to have small variations in their length and hence they do not fit properly. Or you are buying cheap from discount stores and ending up with fakes. That's not meant as criticism, we all need to save money sometimes, but it is an explanation.