Open Settings and open Bluetooth & Devices
See if your mouse is showing there. If it is, click the three dots next to it and choose Remove device.
Now restart your laptop.
After it turns back on, switch your mouse off, wait a few seconds, then turn it on again.
Go back to Bluetooth & Devices, click Add device, choose Bluetooth, and then put your mouse into pairing mode (usually by holding the small button underneath for 3–5 seconds).
When it appears in the list, click it to connect.
Let me know what happens.
Make sure your Bluetooth driver is updated.
If required Uninstall Bluetooth driver by opening Device Manager.
Right-click → Uninstall device
Restart computer (Windows will reinstall driver automatically)