Invalid or missing from / to (use YYYY-MM-DD, UTC days)
Reports or affiliation activity returned 400 when from/to were missing or not valid UTC days (account.invalidDateRangeQuery).
Why this happens
Same family as required/invalid date messages — this is the explicit query-string wording used on member report/activity routes.
Diagnose and fix
1. Include both from and to as YYYY-MM-DD.
2. Prefer the UI date range on My reports / affiliation activity.
3. See order/format siblings if values are present but wrong.
4. See Could not load reports for load failures after a valid range.