Esri introduced a change in the upgrade process at Portal 10.9, "You must also back up extensions for ArcGIS Dashboards or ArcGIS Web AppBuilder. The upgrade will not preserve any extensions you have deployed for these clients. Once your upgrade is complete, you must redeploy your extensions."
If that step was not taken, any existing Web Apps will not load custom widgets correctly.
The property "uri" no longer works for custom widgets, and has been replaced by "itemId". The "itemId" property must reference the ID of the custom widget of the Portal.
- WAB app won't open.
- Error message presented to the user: "Cannot read property 'version' of undefined (reading 'version')
- Using either VertiGIS Studio Item Manager or ArcGIS Online Assistant,
- Update the property "uri" in the config to "itemId", referencing the ID of the custom widget in Portal.