The error code E503 indicates a licensing issue with your institution's iThenticate account. This message appears when your institution's license has expired or has not yet reached its active start date.
How to resolve this error
Since this is a subscription and licensing matter, please contact your iThenticate sales representative or account manager to review and update your institution's license.
Note: iThenticate Technical Support cannot adjust account licenses or resolve E503 errors. Your account administrator or sales representative must assist you with licensing updates.