OK to be clear with this, the visa expired on 23rd May 2017. You had your appointment on 1st June.
Did you put in the FLR M application online before expiry of the visa?
The problem is that on their site, ref
https://visas-immigration.service.gov.u ... nt-booking states under the booking paragraph
"You can choose an appointment up to 45 business days in the future. Appointment times will be based on availability.
If you can’t find an appointment at your preferred premium service centre location before your visa or leave expires, please choose an appointment at a different premium service centre"
Perhaps an oversight on your part which is horrible, but I am sure the admins or others more experienced can help with next steps. Best of luck x