Event Handlers will need to be added to custom forms in order for Alert notification banners to display.
2. Open the Form
4. Add two event handlers.
4.1. Click "+ Add" under the Event Handlers section.
4.2. Enter "FormLoad" as the Function and select the two check boxes.
4.3. Click OK
4.4. Add a second Event Handler with "DebugForm" as the Function.
Note: This Event Handler may already exist and will not need to be added a second time.
5. Save and Publish the form customizations.
9. Select the Entity
10. Hover over the Form and click the edit pen icon.
11. Click the Events tab.
12. Expand the On Load Event Handlers and verify the two Handlers are displaying.
13. Save and Publish the form within the app form designer.
The Alert notification banner will now display on the custom form.