High Sierra 10.13.6: Lost my Bluetooth(Software,Button in the Network/Settings

Hello meinolf64,

If you are having issues using Bluetooth on your Mac, first ensure you are following these steps from Connect a Bluetooth device with your Mac:

1. Make sure the device is turned on.

2. On your Mac, choose Apple menu > System Preferences, then click Bluetooth. Your Mac is now discoverable.

3. Select the device in the list, then click Connect.

If asked, click Accept.

Also, check for any available software updates for your Mac with this article: Update macOS on Mac

If this continues after looking over those, please provide more details on what’s happening and if you are getting an error message of some kind. 

Cheers!