My son (MS, PhD & now publishing at USEPA) said - if no policies at institution - 1) write the paper & then ask that they look at the draft - & in some written form give their OK. Suggest either co-author or a hardy acknowledgement. Their only work is review & approval. He sympathizes w/ you.

I was "co-authored" when I did most of lab work & initial data analysis, but no input on overall design or words about it. I could have been simply acknowledged, but was glad to have the co- authorship.

the issue here is the student is not in contact and isn't responding to contact, they've been sent the full draft but just aren't responding