Waypoints not functioning properly

I installed Omeka into my machine as indicated. Everything worked fine until I installed Neatline-Waypoints widget. I created an exhibit and activated waypoints widget. When I tried to load my exhibits, it returns an error as Could not find file css/payloads/waypoints-editor.css!. I looked back into that directory and find that the file is actually there. I even tried to retype the name and it didn’t work. Adding exclamation mark at the end didn’t work as well. I don’t know what is wrong with this. Can anybody help me! Thank you so much!

My first guess is that the file is not readable by the web server. Check the permissions on all the plugin’s files to make sure the server has read access.