Thanks Heli for your comment.
I think you're right and you found a bug. Hidden courses were added to 'Invalid site element' list in MDL-66806 that affects "Students at risk of dropping out" and some other models, but not "Students who have not accessed the course recently" model. So I've created MDL-71274 issue to fix it. I encourage you to watch, vote or comment on it to add as many information as you can.
Thanks for your help and support!
I think you're right and you found a bug. Hidden courses were added to 'Invalid site element' list in MDL-66806 that affects "Students at risk of dropping out" and some other models, but not "Students who have not accessed the course recently" model. So I've created MDL-71274 issue to fix it. I encourage you to watch, vote or comment on it to add as many information as you can.
Thanks for your help and support!