Imagine this… you’ve lost access to your custom templates for your web apps in ArcGIS Online, now what?? If you try to share a map as an application, and there is no longer an option to choose one of the various application templates provided by ArcGIS Online or other configurable app templates, you may need to reset your templates group.
Indeed this can be frustrating, and nerve racking but we feel your pain and we’ve seen this before. We’ve also heard from our Admin Tools users and have responded to this question a number of times. The following solution has been provided in the Kbase:
Follow the below steps to correct this.
Login to your Organization, and navigate to the "My Organization" page.
Click "Edit Settings"
Click the "Map" tab
Change the "Configurable Apps" Settings back to the Esri default. NOTE: This will change your settings to the ESRI Group. You may also switch it back to one of your other groups if your admin already has a custom template group that should be used.
Click "Save" at the top of the page.