Hi @Alicekings ,
Have you shared proper permission of your SP List to your external users?
Based on the screenshot that you mentioned, it seems to tell that these end users could not sign in SharePoint List with current credential.
When these end users run your shared canvas app including SharePoint Connector, it would ask them to create a connection to SharePoint connector using their own account rather than use your credential.
Note: Your credential used to connect to SharePoint connector would be shared to these end users when you share your app to them
Please make sure you have shared proper permission ("Read Only" permission at least) of your SP List/Library to these end users, then these end users could be able to access your SP List/Library data source from this shared app.
Best regards,
