The option for New Responsive Forms does not appear when opening the Nintex Forms designer.

[#1]

Issue

When opening the Nintex Forms Designer there is no option to select New Responsive Forms.

Resolution

Navigate to site contents in classic mode and look for the Nintex Forms application.
If there is an update available perform the update and test.

If the issue persists, remove the Nintex Forms application from the site and then add it back again.