Hi @GISManager4 ,
Looks like there is an issue with Nearby, Zone Lookup and Sidebar having a custom locator as the only locator service in the org. I was able to reproduce the behavior on my end when I was testing. The team is going to look into the issue.
As a workaround, I think you will need to have the ArcGIS World geocoding service added as a locator in the organization. Then in the app add the custom locator using the search configuration. As for the apps you have already created that are experiencing the issue, I haven't come across a way to get them up and running again so the best way forward is to create a new app and add the custom locator in the search configuration settings.
Thanks!
Sarah