Can’t get mouse to open to change batteries

Press down on the tab on the bottom. Sometimes it sticks, see if you can insert a stiff card into the seam and gently pry it up. Sometimes shaking it a bit also helps.

You might have the same one I do? The manual says, "No user serviceable parts". You may know what you're doing if you can open it, but I don't! LOL. The Magic Mouse 2. Good Luck!