Sorry to hear of the problem you are having.
Is it working fine for you using any default WordPress theme like Twenty Seventeen?
If yes then please activate the Gillion theme again and can you please try temporary enabling WP_DEBUG mode?
To do this, just go to wp-config.php include this:
You might already have a line for WP_DEBUG, so just make sure it’s set to true.
Let me know what errors if any you are getting when you face this issue.