Issue
If the task opens in a browser a SharePoint task form will be presented in either View or Edit mode regardless if a Nintex Responsive form has been added to the task or the appropriate layout has been added to a Nintex classic Form.
Resolution
Additional Information
Click "Link" from the Insert tab ribbon and add a custom link as per the example below.
fn-Replace("{Common:ApprovalUrl}", "Lists/Workflow%20Tasks", "_layouts/15/NintexForms/Mobile")&List=<TaskListId>
Note: Change Workflow%20Tasks to your Task Name and <TaskListId> to your task list id GUID.
The idea for this approach is to use Approval Url which is similar to <SiteURL>/Lists/Workflow%20Tasks/EditForm.aspx?ID=<TaskID>, and replace Lists/Workflow%20Tasks to _layouts/15/NintexForms/Mobile path, to redirect users to the Nintex Form.
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