Disconnect Pics.io from your Google Drive
Open drive.google.com with email@example.com. Open Settings menu:
In the settings dialog switch to 'Manage Apps' tab and find Pics.io application. Press 'Options' dropdown and select 'Disconnect form Google Drive', confirm.
Now open pics.io and press 'Connect Google Drive' button.
In the Google Drive consent choose right account(firstname.lastname@example.org).
That's it, you're done. Now you may do Sync or manually manage the content of your library.