Created a responsive form using Nintex in SP2019. The form contains a Calculated Value control that performs a lookup function. Nothing custom, I just want to display a related column from another list to the user and bring it back to a connected column. Works perfectly fine using the responsive form from the desktop - value is displayed and written back to the connected column.
Actually spoke to my Nintex CSM today and he said this was a known issue. He believes it will be corrected in a new Nintex Mobile iOS app release on Monday, July 26, 2021. We will see!
Thanks for your response!