Too many parallel downloads
The HTML /limit page heading when this viewer already has as many active downloads as their tier allows. Longer body/API strings explain waiting or upgrading (Phase 18).
Why this happens
Simultaneous downloads (ul2_sim_dl_*) slots are full. App or nginx edge concurrency redirects HTML clients here. Guests often have 1 slot; Premium tiers have more.
Diagnose and fix
1. Visitor: wait for a current download to finish, then retry.
2. Admin: raise Simultaneous downloads for that tier (0 = unlimited).
3. See Parallel download limit page and Guest downloads limited at the same time.
4. Not the same as grant rate limits or per-file download count caps.