Queue at most files per batch
The in-page queue is already at the tier cap. Product text: “You can queue at most {maxBatch} files per batch (tier limit). Remove files to add more.”
Why this happens
Client-only guard in addFilesToQueue when room === 0 — queue length already equals ul2_max_batch_*. No API call yet. Cousins: partial add (“Only some files were added…”), truncate-on-submit, and server Upload queue limit reached for your plan.
Diagnose and fix
1. Member: remove finished/queued files, then add more, or upload in multiple batches.
2. Users & limits → Max items per upload (ul2_max_batch_reg / _prem / _prem_pro). 0 = unlimited (with code caps).
3. Per-user override if one account needs a larger queue.
4. Parallel slots (ul2_slots_*) are separate — see File upload slots.