Welcome to the Microsoft Community.
Yesterday, I did a review of the Apple Magic Mouse and in the review, I noted that the device is not natively able to be used with a Windows PC. Though this is true, there is a known workaround out there to help you get the Magic Mouse to effectively work on a PC. I have Windows 10 running perfectly on my I Mac (Boot Camp 3.3) with a magic mouse. Scrolling doesn't work. Need solid, simple help from this community regarding new mouse driver and installation. More ways to shop: Visit an Apple Store, call 1-800-MY-APPLE, or find a reseller.
We apologize for the inconvenience caused to you. I suggest you to check the status of Bluetooth in device manager.
Method 1: Check Device Manager.
Press Windows + X, click on Device Manager.
Check for any exclamation marks in there.
If exclamations mark are there on any device name, try to update them by right clicking on them.
Method 2: Run Hardware and Device troubleshooter.
Magic Mouse For Mac Computer
Press Windows + W, Type troubleshooting.
From the search list, click on troubleshooting
On the left pane, click on view all.
From the list click on hardware and devices troubleshooter.
Follow on screen instructions to complete the troubleshooting.
Follow the steps in the link given below and check if it helps.
Why isn't Windows finding my Bluetooth or other wireless device?
Note: The link above also applies to Windows 10.
Hope the information helps. Let us know if you need further assistance with Windows related issues. We will be happy to help.