I am unable to create a new Shared Connection that I need to use in the 'Start Workflow' action.
The screen turns unclickable but no new window comes up. The below error is shown in the console.
First thing I'd check is if there is an update to the Nintex Workflow App in your tenant. If the app is up to date I suggest you reach out to Nintex Support as the community might not be able to help you with this kind of technical error in Office 365.