Sometimes you may find that you are in some Enterprise Wifi network and you can connect in Windows but not in Ubuntu without CA server certificate.
The following workarounds can help solve the problems:
Open /etc/NetworkManager/system-connections/<WifiName> file with super-user permissions. <WifiName> is the name of Wifi Network( If name if “Corp Wifi”, the file name should be “Corp\ Wifi”) If no such file exist than you have not connected to Wifi yet. Try connecting to Wifi once.
If any prompt comes asking for CA Server Certificate, select Ignore.
Open /etc/NetworkManager/system-connections/<WifiName> file and remove the following line
I found this solution on stackoverflow where this solution was reportedly not working on 14.04.
For 14.04 instead of removing complete line,
Change the line to
The second solution for 14.04 worked for me. If any of the solution is not working then please comment below.