Custom Sidebars Pro is Hanging

I've recently moved a site to a new domain. Since doing so, I can't get Custom Sidebars Pro to work. Every time I try to create a new sidebar, edit a sidebar, delete a sidebar or import sidebars, the modal window status wheel just spins and spins.

I checked Chrome for console errors and got this:

Failed to load resource: the server responded with a status of 404 (Not found) http://www.americansolarandroofing.com/wp-content/plugins/custom-sidebars/inc/external/wpmu-lib/js/wpmu-ui.min.js.map
Uncaught TypeError: undefined is not a function widgets.php:22172(anonymous function) widgets.php:22172n.event.dispatch load-scripts.php?c=1&load%5B%5D=jquery-core,jquery-migrate,utils&ver=3.9.2:3r.handle load-scripts.php?c=1&load%5B%5D=jquery-core,jquery-migrate,utils&ver=3.9.2:3n.event.trigger load-scripts.php?c=1&load%5B%5D=jquery-core,jquery-migrate,utils&ver=3.9.2:3e.event.trigger load-scripts.php?c=1&load%5B%5D=jquery-core,jquery-migrate,utils&ver=3.9.2:8x load-scripts.php?c=1&load%5B%5D=jquery-core,jquery-migrate,utils&ver=3.9.2:4b load-scripts.php?c=1&load%5B%5D=jquery-core,jquery-migrate,utils&ver=3.9.2:4
GET http://www.americansolarandroofing.com/wp-content/plugins/custom-sidebars/inc/external/wpmu-lib/js/wpmu-ui.min.js.map 404 (Not found) /wp-content/plugins/custom-sidebars/inc/external/wpmu-lib/js/wpmu-ui.min.js.map:1