Bluetooth Mouse not detected after a reboot

This Microsoft Support article might help: Resolve Bluetooth mouse or keyboard failure to function.

The article contains 6 possible fixes or tests. Even if none of them helps, of special interest is the section named "Method 4: Locate the Wireless Link icon in Control Panel, and then reestablish the link with the wireless device".

It would help if you could report on what you saw when following this Method 4, maybe even adding screenshots for specially interesting info.

For me the thing that solved this issue was: in Windows Services find service "Bluetooth Support Service" and make sure it is in "Auto" launch mode and is started by "System" (first option without a textbox to enter user name). Source: Microsoft support