SLA Not appearing on Ticket

We have 2 SLAs set up on our service desk - Time to first Response, Time to resolution. The settings are in the attachements SLA1.png & SLA2.png. We are setting the system up to create tickets from emails and have set up a default email handler so users in the system are not created.

When we reply to emails (via our email client) to the customer, with the support email address included this satisfiues the Time to first Response SLA. The comment is added to the ticket as expected, but we are no longer able to see the Time to first Response SLA - as shown in the attachment - SLA Missing.png