@munmun If you already have the app installed in your tenant before july 1st on another site you should still be able to add the app to new or existing sites(https://learn.microsoft.com/en-au/sharepoint/dev/sp-add-ins/add-ins-and-azure-acs-retirements-faq).  There was a bug where it was not possible to add the app but that should be resolved. So if you have the app installed, I would suggest reaching out to Nintex and Microsoft Support. If you never had the app installed you would need to use the new SPFx app instead(https://help.nintex.com/en-US/nwc/Content/Settings/NintexAutomationCloudApp.htm).

Hi @munmun 

Has your issue been resolved?