I have the problem on an old (2008) Sony Vaio VGN FW5 that the wifi is blocked by a switch. In Windows, I used to use a wifi dongle, however the dongle is now also blocked by the hardware switch in Ubuntu 14.04 LTS. I also had this problem in 16.04 but tried to solve by going back to 14.04. I have tried the solution suggested by blacklisting the kernel driver for the internal wifi card but the problem persists.
rfkill lists the dongle as not hard or soft blocked but the network manager still lists it as deactivated by hardware switch.
Is there anything else I could try?