Cause
threshold_days for milestone.due_soon or deadline.due_soon must be 1, 3, 7, 15 or 30.
What to do
Choose one of those values or send {} to return to the default threshold (7 days for a milestone, 3 for a deadline).
application/problem+json
{
"type": "https://masnet.com/developers/errors/invalid_threshold_days",
"title": "Invalid notice threshold",
"status": 400,
"detail": "...",
"code": "invalid_threshold_days",
"correlation_id": "..."
}