Too many uploads in progress
The member already has as many pending uploads as their plan’s parallel slots allow. Full text asks them to wait for a current upload to finish.
Why this happens
ul2_slots_* caps how many non-folder pending files can exist at once. Checked when starting a new upload (after the batch/queue depth check). Stale pendings are often released after ~15 minutes idle. If nginx edge slot limiting is on, the gateway may return a shorter “Too many uploads in progress” instead.
Diagnose and fix
1. Member: let an upload finish, or cancel stuck items, then retry.
2. Admin → Settings → Users & limits → File upload slots (ul2_slots_reg / _prem / _prem_pro). 0 = unlimited.
3. Per-user override if only one account needs more parallel uploads.
4. Check for stuck pending rows; cancel or wait for stale release.
5. Do not confuse with Upload queue limit (ul2_max_batch_* = how many pending total) or hourly Too many uploads rate limits.