This is a weird issue in Mint Ubuntu gnome that I've only seen on one system. It may happen in your terminal or your browser but one program will just refuse to allow input from the keyboard. I am not sure if it's some weird fluke on a strange keyboard by perhaps accidentally hitting a weird key combination.
This seems to be because of the iBus language detector app that shows as your language in the panel eg. EN. After closing it the program with the issue was able to type and receive keyboard input again.