Dear friend, I have not yet received your education certificate. Your institution indicated that I would recieve the certificate by [enter the date]. I sent a text message to this effect, but I'm not sure if you recieved it. When the certificate arrives, I will inform you of its arrival.
Didyou want the recipient to contact their institution? Is there an implicit request for the recipient to do something about this problem? If so, consider letting them know what you need from them. Also, consider using their actual name, rather than friend.
I hope this is helpful.
p.s. I am not a teacher, but I am a native English speaker and a professional writer and editor.
Student or Learner