I just noticed a conflict between the 'Custom Sidebars Pro' plugin and the 'Q2W3 Fixed Widget.'
When both plugins are activated, I receive a 'Warning' message. Picture is attached for reference! When this warning message is displayed, the custom sidebars will not appear. I've found that deactivating the 'Q2W3 Fixed Widget' will result in the custom sidebars displaying on the site.
Does anyone have any experience with both plugins? I've reached out to WPMU support and I am waiting for a reply!