[Plugin: Show Ads Dynamically] first plugin & need help troubleshooting

I’m not an exceptional coder, but I wanted to try creating my first plugin for my wordpress site iamsarahkohl.com

The goal of the plugin would be to take user inputs from the settings page, then show them based on the screen width on a wordpress post or widget with the use of a shortcode.

I read through the documentation and I’ve been able to upload and activate my plugin without errors, however when I go to use the shortcode the banners aren’t displayed, only the shortcode text.

I’m not really sure how to troubleshoot the issue, and despite searching I can’t seem to find help so I thought I would make a post. My plugin file is on pastebin if anyone has the time to review it for me.