Plan allows this many downloads at once
/limit body for signed-in viewers: your plan allows up to {allowance} downloads at the same time — try again after about 5 seconds.
Why this happens
Simultaneous downloads (ul2_sim_dl_*) are full. Same situation as Too many parallel downloads for your account / for your plan, shown as friendly HTML. Guests see Guest downloads limited at the same time.
Diagnose and fix
1. Wait for an active download to finish, then retry.
2. Admin: raise Simultaneous downloads for that tier.
3. Upgrade CTA may appear when higher tiers have more slots.
4. Distinct from rolling count limits (#5–7) and grant rate limits.