Why has the connection from the computer to my smart tv all of a sudden stop working?

Is the TV set to get the signal from the proper input, i.e. if using a cable to HDMI1 on TV is HDMI 1 selected on TV as input source?
 


 
It is the proper cable listed in the manual. I've tried everything. Naturally, when attempting to connect I use HDMI as the source. It worked perfectly for 3 weeks and then quit connecting.