I´m still having problems with certificate on v.1.9.2.
I downloaded both again yesterday, so they are recent versions.
The generated certificade does not show de quiz grades. It left the space needed but the grade doesn´t apear.
I have also installed this module on 1.9.2 (soon to be upgraded) and there is nothing displayed against the grade
I realised that if you login as the admin the system will allow you to view a certificate even if you have not even attempted the quiz.
Therefore no attempt no grade.