Too many parallel downloads for your account
A signed-in member already has as many active downloads as their plan allows. Product text: wait until your current download finishes (429 on grant/stream).
Why this happens
ul2_sim_dl_reg / _prem / _prem_pro leases for u:{userId} are full. HTML clients may be redirected to /limit with plan-oriented meta copy instead.
Diagnose and fix
1. Member: pause or finish a download, wait a few seconds, retry.
2. Admin: raise Simultaneous downloads for that tier (0 = unlimited).
3. Per-user override if one account needs more slots.
4. Guests see the guest parallel messages instead.