Ubuntu 18.04: Bluetooth device disconnects right after connect on Lenovo P50

I had the same issue and solved it with the following steps:

sudo apt-get install pulseaudio-module-bluetooth

killall pulseaudio

Try to connect again.

Solution source

I ran into this issue on my Lenovo P51 running Ubuntu 18.04, and I discovered that the pactl module "module-bluetooth-discover" was not loading properly at boot time. I fixed the issue by replacing it with "module-bluez5-discover" in my pulse configuration.

You can test this by running:
sudo pactl unload-module module-bluetooth-discover
sudo pactl load-module module-bluez5-discover

And try to repair/reconnect your devices. If it works, replicate the following configuration in your /etc/pulse/default.pa config.

# Modify: /etc/pulse/default.pa
# Comment out the following line

.ifexists module-bluetooth-discover.so
load-module module-bluetooth-discover
.endif

# Replace it with ...

.ifexists module-bluez5-discover.so
load-module module-bluez5-discover
.endif

My suspicion is that this is a change that was made during the switch from Unity to Gnome and the leftover configurations remained, leaving the standard Bluetooth modules behind which don't load correctly.

After switching to bluez5, I have since had no issues, and Bluetooth connects without complaint on my mobile phone, mouse, and headset. :)

EDIT: I also followed several steps mentioned here: Bluetooth doesn't work after resuming from sleep, Ubuntu 18.04 LTS

To exactly replicate my configuration, make sure you apt-get install bluez blueman pulseaudio to have all the same packages. As was suggested in the referenced problem, I believe this was caused by upgrading to 18.04 from 17.04.

I also have this problem with my NC75 Pro headset from time to time. Dark Singularity's answer and ubuntu upgrade did not work for me.

The only workaround I found is to remove the device and install it again:

If it won't connect at all, maybe you have to update the driver as explained here.

The solution which has worked for months, was to upgrade to a newer version of bluez, as described here: Bluetooth doesn't work after resuming from sleep, Ubuntu 18.04 LTS. But recently I experienced regression: I get the same behaviour as before. But in an attempt to solve it, I downgraded to an old version of bluez and later upgraded back to the same version that stopped working properly (5.50-0ubuntu0ppa1 in my case) which solved the problem for now. So reinstalling seems to fix or mitigate something. Seems likely this can happen again sometime in the future ...

I have the same issue with 20.04. I've posted my workaround in the following question, but unfortunately haven't found a complete solution:

Ubuntu 20.04 + Gnome 3.36.8: Bluetooth headset disconnects straight after connect

Install pulseaudio-module-bluetooth:

sudo apt install pulseaudio-module-bluetooth

Then restart pulseaudio:

pulseaudio -k ; pulseaudio -D

Finally, try connecting again in the Bluetooth manager. You might also need to change some sound settings (type "sound" into the main menu) or reload the tab/program playing audio for everything to work properly.

1. Remove the device on Pulse Audio Bluetooth Devices

2. Kill pulse audio and restart the Bluetooth service

sudo killall pulseaudio && sudo service bluetooth restart