Hi Oscar. I'm Greg, 10 years awarded Windows MVP, specializing in Installation, Performance, Troubleshooting and Activation, here to help you.
Try these fixes for cannot pair Bluetooth Surface Mouse:
https://windowsreport.com/bluetooth-mouse-not-w... (Avoid ad links which intrude into editorial copy, especially avoid Restoro and Reimage ads)
https://www.easypcmod.com/how-to-fix-bluetooth-...
https://e-methodstechnologies.com/fix-microsoft...
https://tencomputer.com/bluetooth-mouse-not-wor...
https://answers.microsoft.com/en-us/surface/for...
https://www.youtube.com/watch?v=8R4D0zEglzs
I hope this helps. Feel free to ask back any questions. Please report back results for all steps given so I know what else to suggest if necessary.
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