I contacted them via Line, initially they just said to follow the Songkhla Vaccination website advise, then they sent another message confirming the date and pointing out the venue had changed.
Got confirmation via BHH Line for 21 Oct 2021 but note it's not at the Senanarong Camp Club, the location has been switched to Convention Room, 4th floor, Bangkok Hospital Hat Yai.
Whatsapp wouldn't load on my laptop yesterday too, but I just downloaded and reinstalled over the existing installation and it was working fine.
https://www.whatsapp.com/download/
It's just totally disorganised, they keep switching the direction of the vaccine supply 'hose'. I didn't get my second AZ jab today either. Meanwhile my wife, whose been signed up since start July, has had Covid whilst waiting for an appointment.