It sounds like something went wrong during the upgrade and you have somehow ended up with a corrupted file or duplicate versions of the plugin or duplicate files within your installation. It’s a little difficult for me to see what has happened without having access to your site.
I recommend deleting the plugin altogether, then going into your cPanel or using an FTP client to check there aren’t any leftover files or directories related to tinyWYM. Then try re-installing the plugin fresh from your WP Admin area.
I’m sorry you are have this problem. I’ll make sure we get to the bottom of it.