Sorry @Aman1 ,,
This is one of those things that happens ( trying a new OS ) i had to install several times, from tinkering. 
So download anything you wish to keep from the pc, See attached " How to ".
After that , first try these below commands ( One at a time ) & see if any of them work.
1st:
Try this,
reboot & try.
If not try this next:
sudo apt install --reinstall gnome-control-center
then
reboot.
Try again,
If not, Try
sudo apt install --reinstall gnome-shell-extension-ubuntu-bluetooth
then
reboot.
Hope one works.
Please let us know how you go.
If none of the above work, Then it will need to be a new install.
If you wish to keep added programs etc, follow this link Before installing.