Error "The given key was not present in the dictionary" in Nintex Form for Office 365

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When opening the Nintex Form for Office 365, the following error may occur:
The given key was not present in the dictionary.

Verify that the SharePoint Online List / Library setting for the Lookup data type column has a valid reference to the other List.

When creating a SharePoint List / Library from a list template, the reference for the Lookup column might be lost.

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