Hi Alan Nankervis,
Thank you for reaching out Microsoft Community. We thank you for checking some fixes for this issue and we apologize for the inconvenience this may have caused you.
If the Microsoft Arc Mouse is currently showing paired to your Surface device, please do unpair it and do the following steps:
Open Device Manager
Expand Bluetooth
Right-click on drivers available under Bluetooth and uninstall everything, then restart your Surface.
After it restarted, go to Download driver and firmware for Surface, choose Surface Laptop 3, then choose the right processor to download the right driver pack for your Surface laptop 3, click Download on the next page.
Choose the .msi file that matches your current OS Build or the one closest to the current build of your Surface device and click Next to reinstall the Bluetooth drivers. ( That OS build you are to install contains those Bluetooth drivers you uninstalled earlier ).
After downloading, run and install the .msi then Restart. Re-pair your Microsoft Arc Mouse and see if this works fine this time.
If this helps, please let our Community know by marking this post as an answer. Otherwise, don't hesitate to respond to this thread.
Kind Regards,
Crest_Z