Bluetooth is what Macs use to connect wireless devices like keyboards, mice, trackpads, speakers, and other peripherals. Generally, this is a solid technique. But at some point, you may experience difficulty establishing a Bluetooth connection with one or more devices.
Most issues can be resolved by unpairing and repairing the Bluetooth device, replacing its battery, restarting the Mac, or performing an SMC reset. However, if none of these methods work, you can always try resetting your Mac's Bluetooth module. Here's how to do it in macOS using the hidden Bluetooth Debug menu.
How to Reset a Mac's Bluetooth Module
Before proceeding, keep in mind that if your setup relies solely on bluetooth to communicate with your keyboard and mouse, you'll be temporarily disconnecting from them using the method below, so you may want a backup wired input device option just in case.
1. While holding down the Shift + Option (Alt) keys on your Mac keyboard, click the Bluetooth symbol in the upper right corner of the macOS menu bar. (If you don't see it there, you need to check Show Bluetooth menu bar in System Preferences -> Bluetooth.)
2. Locate the Debug submenu that is displayed and hover your mouse cursor over it. 3. Click Reset Bluetooth Module.
4. Now, restart your Mac.
You'll notice a couple of other potentially useful options in the Debug submenu. After a factory reset, all connected Apple devices will do exactly what they say they should - forcing all Apple-branded Bluetooth accessories back to the default settings that came with them at the factory. It's a solid fallback option if you've tried everything else to fix connection issues, including resetting the bluetooth module.
Finally, the "Remove All Devices" option can be useful if, for example, you want to move your Bluetooth mouse and keyboard to another Mac. However, devices can also be removed individually from the macOS menu bar, as long as you hold down Shift+Option (Alt) before clicking the Bluetooth symbol.
Removing the device this way means you also don't eliminate any other established Bluetooth connections you may wish to keep, such as speakers and the like.