Hi Melanie,
I hope you are well today and thanks for posting on the forum.
Your site is displaying JavaScript error message as you have mentioned in the following reply that may be causing this issue.
https://www.ads-software.com/support/topic/create-new-sidebar-keeps-loading?replies=8#post-6487116
You can just try on your development site using default WordPress theme like Twenty Fifteen and deactivating all other plugins as displayed in the following flowchart to know which theme/plugin is generating this error message and causing the Custom Sidebars plugin not to work.
https://premium.wpmudev.org/wp-content/uploads/2013/12/Support-Process-Support-Process.png
Please let me know what is generating this error message by troubleshooting it as described above so that we can resolve this issue.
If you please also share me your site URL.
Best Regards,
Vinod Dalvi
