VirtualBox : Configuration error: Failed to get the MAC value (VERR_CFGM_VALUE_NOT_FOUND)

I am running Ubuntu 18.04 on VirtualBox, everything was working fine,
until I started fiddling with Network configuration to access my webserver from my host Windows machine.
Since then I am getting the below error while trying to start the VM.
I have no clue why this is happening

Failed to open a session for the virtual machine Lab (Ubuntu 18.04.4).

Configuration error: Failed to get the "MAC" value (VERR_CFGM_VALUE_NOT_FOUND).

Result Code: E_FAIL (0x80004005)
Component: ConsoleWrap
Interface: IConsole {872da645-4a9b-1727-bee2-5585105b9eed}