Bluetooth is not working ubuntu 18.04 LTS

I had the same problem and found this:

"A brilliant developer named Takashi Iwai came up with a solution that I incorporated into the 4.15 kernel

sudo apt install git build-essential dkms
git clone https://github.com/jeremyb31/newbtfix-4.15.git
sudo dkms add ./newbtfix-4.15
sudo dkms install btusb/4.0

Reboot"

Found here ubuntu 18.04 LTS bluetooth discovery not working

I had to install git manually from Synaptic. I don't understand what it does, but it worked for me.

I partially fixed the problem running the following commands:

sudo apt-get install build-essential git
git clone https://github.com/lwfinger/rtlwifi_new/
cd rtlwifi_new
make
sudo make install
echo "options rtl8723be fwlps=0" | sudo tee /etc/modprobe.d/rtl8723be.conf

you might face a problem of a slow wifi connection after that, I fixed it with following commands:

sudo modprobe -r iwlwifi sudo modprobe iwlwifi 11n_disable=1
echo "options iwlwifi 11n_disable=1" | sudo tee /etc/modprobe.d/iwlwifi.conf

IMPORTANT: This did not fix the problem totally, I have to close wifi, search and pair bluetooth device then open wifi again. I don't know exactly why is this happening but googling told me that ubuntu drivers are problematic with rtl8723b adapters like mine

I had the same problem after upgrading the system. I found following error in /var/log/dpkg.log :

2019-03-23 16:37:24 status half-configured pulseaudio-module-bluetooth:amd64 1:11.1-1ubuntu7.1
2019-03-23 16:37:24 status half-installed pulseaudio-module-bluetooth:amd64 1:11.1-1ubuntu7.1
2019-03-23 16:37:24 status config-files pulseaudio-module-bluetooth:amd64 1:11.1-1ubuntu7.1
2019-03-23 16:37:24 status config-files pulseaudio-module-bluetooth:amd64 1:11.1-1ubuntu7.1
2019-03-23 16:37:24 status config-files pulseaudio-module-bluetooth:amd64 1:11.1-1ubuntu7.1
2019-03-23 16:37:24 status not-installed pulseaudio-module-bluetooth:amd64 <none>

So I reinstalled the package, and restarted pulseaudio, which finally solved the problem:

sudo apt-get install --reinstall pulseaudio-module-bluetooth
pulseaudio -k
sudo alsa force-reload