SFTP upload disabled on this site
SFTP is blocked for everyone because the site master switch (or plugin entitlement) is off — not because of one member’s plan.
Why this happens
assertMemberSftpUploadAllowedBySiteLimits hits the site-mod branch: toggle.sftp_mod false/unset, or the SFTP premium plugin is not entitled. Tier ul2_ftp_on_* switches do not matter until the site mod is on. Distinct from plan-blocked (SFTP upload not enabled for your plan).
Diagnose and fix
1. Admin → Settings → Mods → SFTP (toggle.sftp_mod) — turn on.
2. Confirm the SFTP premium plugin is installed/licensed.
3. Then enable FTP for the tiers that should use it (toggle.ul2_ftp_on_*).
4. Still enable ingest on at least one server under Servers.