Error "Object Reference not set to instance of an object" Editing Task Form for Flexi Task
When editing a Nintex Task Form for a Flexi Task, the form cannot be opened or edited and the following error occurs:
Object Reference not set to instance of an object
Upgrade to Nintex Forms 2.8.1 or later version.
If the template is available in the list at the bottom of the device layout page:
Open the platform that does not currently have the 'Use Template' box checked.
Check the 'use template' box.
If the template is unavailable in the list:
Create a new Nintex Form (on a new list preferable).
Select all missing platforms in CA from the top ribbon of the form.
Export the form.
Upload the exported form in the template section of CA.
Verify that the platforms are now available in the list below.
Verify that the 'Use Template' box is now checked (check it using the steps above if it is not).
This issue can be caused by missing forms templates (Mobile or Phone platform typically) in Central Administration > Nintex Forms Management > Manage Device Layouts. The 'Use Template' boxes for the missing template will be unchecked, and the available templates list at the bottom of the page will not include that platform.