Oldtimer 4 years and counting

[Treasur]

Yup, had one of these. Best guesses? Shame, guilt, confusion, teenagers hate paperwork, worried that they will expose secrets or what a mess they're in, think of themselves as 'done' already so not a priority...

In the end, the reasons don't matter. Assume he won't participate and either a) use it to avoid D if that's what you want or b)accept that anything that needs adult collaboration is a waste of time and put the pressure on timescales with significant consequences.