Hi Kate,
A couple of things…
1) Seems like you are holding too many copies of the plugin on your server, or at least, the plugin’s folder has been renamed, unfortunately. As per the error below, the plugin tries to load files from the directory called “tweet-wheel-pro-4” whereas it should simply be “tweet-wheel-pro”. If you navigate to wp-content/plugins, you will see what I mean.

2) The above also causes the following error. Plugin files either can’t be loaded because of the wrong directory name or they haven’t been uploaded to the server.

Happy to fix this for you if you let me have FTP login details. Otherwise, let me know if you need me to explain anything. To recap:
1) Go to WP admin and deactivate (don’t uninstall) all Tweet Wheel instances.
2) Use your FTP to navigate to wp-content/plugins and delete any tweet-wheel folder you have there.
3) Upload the fresh copy of the plugin and make sure the folder’s name is “tweet-wheel-pro”.
4) Go back to WP Admin and activate Tweet Wheel.
Thanks