How to reset network manager

You can restart network-manager by doing (in the terminal):

sudo service network-manager restart

Certainly I find this can help with some network hardware issues (network-manager seems not to properly detect when my wifi is turned back on with an external switch, for instance), whether it will help here you will have to find out.

In addition to @chronitis, if your machine faces this problem more often, then you can create an alias in your UNIX based machine like reset-wifi. This will save your good mood and time.

$ echo "alias reset-wifi='sudo /etc/init.d/network-manager restart'" >> ~/.bash_aliases

This works for my machine: Ubuntu 16.04 LTS. Make sure you open new instance(new tab) of the terminal Emulator to check if the alias works.

Now everytime, you can reset using a single command.

john@john-Inspiron-7347 ~> reset-wifi 
  [sudo] password for john: 
  [ ok ] Restarting network-manager (via systemctl): network-manager.service.