Atom file does not seem to work

Hi,
I am a beginner and have recently started to learn Python.

The atom file does not seem to work after 1st day. I am able to type the program, but the reserve words, variables, operators do not show different colours (as was happening on the 1st day). And when I check for the program on python, the program does not run.

Any suggestions to make this work are welcome.

Thanks in advance!