If you are receiving the error message 'Hmm ... we couldn't find that. Please make sure you've entered the correct URL' when trying to submit to Turnitin via a direct submission link, it is likely that the expiry date and time of the link has passed, meaning it is now expired and cannot be used to submit.
Please contact your instructor if you require further assistance, as they will be able to confirm if the submission link has expired and provide you with an alternative link if necessary.