URL in the Email Template isn't working

Hi team, I am observing a change in behaviour. When a field {opportunity.Link} is used in email template to include the record link in the email, It worked completely fine. When a partner user clicked on the URL, it would redirect to partner portal page successfully. Till last month it worked fine but this month the URL isn't working and throwing the error. Although the user has access to the record, object and no changes made on the template. May I know if salesforce has introduced anything new related to template URLs? Or is there any other reason?

#Sales Cloud  #Trailhead  #Salesforce Developer  #Email Template  #Salesforce Admin  #Salesforce