My headset connects and then immediately disconnects

Bluetooth headset - Device connects, then disconnects after a few moments - ArchWiki

If you see messages like the following in the journal, and your device fails to connect or disconnects shortly after connecting:

bluetoothd: Unable to get connect data for Headset Voice gateway: getpeername: Transport endpoint is not connected (107) 
bluetoothd: connect error: Connection refused (111)

This may be because you have already paired the device with another operating system using the same bluetooth adapter (e.g., dual-booting). Some devices cannot handle multiple pairings associated with the same MAC address (i.e., bluetooth adapter). You can fix this by re-pairing the device. Start by removing the device:

$ bluetoothctl
[bluetooth]# devices
Device XX:XX:XX:XX:XX:XX My Device 
[bluetooth]# remove XX:XX:XX:XX:XX:XX

Then restart bluetooth.service [ systemctl restart bluetooth.service], turn on your bluetooth adapter, make your device discoverable, re-scan for devices, and re-pair your device. Depending on your bluetooth manager, you may need to perform a full reboot in order to re-discover the device.