macOS No Longer Connecting to Wireless Keyboard Wirelessly

Question

I have an Apple Magic Keyboard with Numeric Keypad, and normally it works well wirelessly, and was doing so this morning, but suddenly it's no longer working.

The keyboard still works perfectly via its cable, through which it is now fully charged, however upon disconnecting the cable it is disconnected from the computer completely, despite the power still being on, and Bluetooth being enabled on the computer (a 2018 Mac-Mini).

I've tested the keyboard with another machine, and it still works as expected, so there appears to be no fault with the keyboard itself. On the other machine, disconnecting the cable causes it to connect automatically via Bluetooth like it's supposed to. But for some reason this isn't happening on my brand new Mac-Mini (which has been working fine for about two weeks until today).

To try and rule out a hardware fault, I tried using a USB Bluetooth dongle to see if I could connect the keyboard using that, but have had no more success with that than with the internal Bluetooth.

I installed Bluetooth Explorer (from the Xcode additional tools) to make sure I had switched to the USB dongle, but have avoided using any of its other functions; however, I've noticed two errors in its event log:

updateChainPower error: 82
(null) (Handle: 0xB) connection failed, status: 0x04

The first occurs upon opening Bluetooth Explorer's Bluetooth Status window, while the second occurs when attempting to connect to my keyboard wirelessly.

Given that the keyboard works fine with another machine, and a USB Bluetooth Dongle cannot connect either, this seems like it may be a software issue with macOS. It's like there's just no signal.

Other steps I've already tried include:

1. Clearing all devices and re-pairing the keyboard (connecting via cable).
2. Turning Bluetooth off, trashing /Library/Preferences/com.apple.Bluetooth.plist then restarting.
3. Resetting the Bluetooth module via the debug menu (Option-Click Bluetooth menubar widget).
4. I've also tried to pair my Mac with my Android phone but neither is able to detect the other (with or without the USB dongle).
5. Reset NVRAM
6. Reset SMC
7. Booted in Safe Mode (no change even after re-pairing)
8. Tested whether Bluetooth worked under Recovery (it didn't)

Are there any other possible fixes for this issue?

Edit: I'm running macOS Catalina 10.15.1 on a 2018 Mac-Mini

Bluetooth System Report

I removed all MAC addresses, but of possible note are the multiple Miscellaneous/Unknown devices, including one named "Haravikk's Mac" but which has a different MAC address from that listed at the top (under features and settings).

Apple Bluetooth Software Version:    7.0.1f1
Hardware, Features and Settings:
    Name:    Haravikk's Mac
    Address:    ##-##-##-##-##-##
    Bluetooth Low Energy Supported:    Yes
    Handoff Supported:    Yes
    Instant Hot Spot Supported:    Yes
    Manufacturer:    Broadcom
    Transport:    UART
    Chipset:    4364B0
    Firmware Version:    v86 c4406
    Bluetooth Power:    On
    Discoverable:    Off
    Connectable:    Yes
    Auto Seek Pointing:    On
    Remote wake:    On
    Vendor ID:    0x05AC
    Product ID:    0x007B
    Bluetooth Core Spec:    5.0 (0x9)
    HCI Revision:    0x1136
    LMP Version:    5.0 (0x9)
    LMP Subversion:    0x1056
    Device Type (Major):    Computer
    Device Type (Complete):    Mac Desktop
    Composite Class Of Device:    0x380104
    Device Class (Major):    0x01
    Device Class (Minor):    0x01
    Service Class:    0x1C0
    Auto Seek Keyboard:    On
Devices (Paired, Configured, etc.):
    ##-##-##-##-##-##:
        Address:    ##-##-##-##-##-##
        Major Type:    Miscellaneous
        Minor Type:    Unknown
        Services:
        Paired:    Yes
        Configured:    Yes
        Connected:    No
        Bluetooth Core Spec:    1.0b
        Class of Device:    0x00 0x00 0x0000
    ##-##-##-##-##-##:
        Address:    ##-##-##-##-##-##
        Major Type:    Miscellaneous
        Minor Type:    Unknown
        Services:
        Paired:    Yes
        Configured:    Yes
        Connected:    No
        Bluetooth Core Spec:    1.0b
        Class of Device:    0x00 0x00 0x0000
    Haravikk's Mac:
        Address:    ##-##-##-##-##-##
        Major Type:    Miscellaneous
        Minor Type:    Unknown
        Services:
        Paired:    No
        Configured:    Yes
        Connected:    No
        Bluetooth Core Spec:    1.0b
        Class of Device:    0x00 0x00 0x0000
    ##-##-##-##-##-##:
        Address:    ##-##-##-##-##-##
        Major Type:    Miscellaneous
        Minor Type:    Unknown
        Services:
        Paired:    Yes
        Configured:    Yes
        Connected:    No
        Bluetooth Core Spec:    1.0b
        Class of Device:    0x00 0x00 0x0000
    Magic Keyboard with Numeric Keypad:
        Address:    ##-##-##-##-##-##
        Major Type:    Peripheral
        Minor Type:    Keyboard
        Services:
        Paired:    Yes
        Configured:    Yes
        Connected:    No
        Bluetooth Core Spec:    1.0b
        Vendor ID:    0x004C
        Product ID:    0x026C
        Class of Device:    0x05 0x10 0x2540
    Services:
        Bluetooth File Transfer:
            Folder other devices can browse:    ~/Public
            When receiving items:    Accept all without warning
            State:    Disabled
        Bluetooth File Exchange:
            Folder for accepted items:    ~/Downloads
            When other items are accepted:    Save to location
            When receiving items:    Accept all without warning
            State:    Disabled
        Bluetooth Internet Sharing:
            State:    Disabled
    Incoming Serial Ports:
        Bluetooth-Incoming-Port:
            RFCOMM Channel:    3
            Requires Authentication:    No

Answer 1

Since you have tried already trashing Bluetooth .plist file, you can try to follow three basic steps to release some kernel panic of the macOS which might fix your issue as the keyboard is working on other devices.

Reset NVRAM or PRAM on your Mac

Shut down your Mac, then turn it on and immediately press and hold these four keys together: Option, Command, P, and R.

You can release the keys after about 20 seconds, during which your Mac might appear to restart.

Test after this.

If this doesn't help then at last try to:

Reset the SMC on Mac

First, shut down your Mac and Press Shift-Control-Option on the left side of the built-in keyboard, then press the power button at the same time. Hold these keys and the power button for 10 seconds. Release all keys. And, Press the power button again to turn on your Mac.

Start up in safe mode

Start or restart your Mac, then immediately press and hold the Shift key. The Apple logo appears on your display.

Release the Shift key when you see the login window. If your startup disk is encrypted with FileVault, you might be asked to log in twice: once to unlock the startup disk, and again to log in to the Finder.

To leave safe mode, restart your Mac without pressing any keys during startup.

This will release some kernel panic that might help to fix your issue too.