IPv6 literal URLs not supported
Remote URL upload does not accept URLs whose host is an IPv6 literal (for example https://[2001:db8::1]/file.zip).
Why this happens
Host safety checks for remote import only allow normal hostnames and public IPv4 targets. A hostname containing : (IPv6 literal form) is rejected up front. Hosts that resolve only to IPv6 (no A record) are blocked with a related “no IPv4” style message.
This is not a batch limit or plan size issue.
Diagnose and fix
1. Member: paste a URL with a normal hostname (https://cdn.example.com/file.zip) or a public IPv4 URL — not a bracketed IPv6 address.
2. If their only mirror is IPv6-only, host the file somewhere with IPv4, or upload via browser / SFTP instead.
3. Admin: Remote URL still needs Mods → Remote URL upload on and the tier not blocked.
4. DNS check from the app server: dig +short A example.com — confirm an IPv4 answer exists when using a hostname.