My web app access to a shared spreadsheet via a Google Service Account was working perfectly. This was enabled by adding the service account email (@.iam.gserviceaccount.com) as a user email in the doc sharing dialog.
At some point opening the spread sheet in google drive popped up a sharing dialog with a message about external access being turned off. The admin says they made no changes yet my app code to access the spreadsheet now fails with a "access denied " error.
How can I restore access to this spreadsheet from my service account? I've search the web with no answers forthcoming. idon;t have admin access to so need ot explain to the admin.
Is it possible to do so without enabling global external access? We want to remain secure.