If you're applying for masters/post graduate diploma - Include most recent post secondary education (transcript, certificate and individual marksheets including one with backlogs).
if you are applying for bachelors/diploma - Include your secondary education (marksheets, transcript and certificate).
They normally give away missing marksheets as reason for refusal where you do not include backlog marksheets.
In your particular case, VO couldn't find your masters marksheets, so anything you claim on the application form where you need to provide your education and work history, you need to attach supporting evidence. Since you already have declared your masters in your initial application. You now need to attach your masters + bachelors degree transcript, marksheets (including ones with backlog) and degree certificate.
Working as a internet freelancer is not considered as concrete work experience, unless you were making as good as a full-time job candidate in your field of interest. You need to have some verifiable work experience along with evidence. You need to showcase that you have some experience in home country though you are having trouble progressing further in your career due to lack of appropriate education/experties. You need to also explain in your SOP things such as why is your existing masters not sufficient, and why gaining whatever course you intend to do in Canada and how it provides you with additional knowledge than your existing masters degree.
VO had also spoken about availability of similar program in home country, so you would wanna highlight/compare what programs you locally have available and how dropping affordable education in your home country and attaining highly expensive Canadian education is important at this point.
