Host has no IPv4 address for remote upload
The remote host resolved, but only to IPv6 (AAAA). Remote upload currently fetches via IPv4 only, so AAAA-only hosts are blocked.
Why this happens
assertRemoteUrlHostSafe requires at least one DNS A record. The pinned fetch connects by IPv4. IPv6 literal URLs are a separate rejection (IPv6 literal URLs not supported).
Diagnose and fix
1. Member: use a hostname that has an A record, or a public IPv4 URL.
2. From the app server: dig +short A example.com — empty A + only AAAA explains this error.
3. Work around: host the file on an IPv4-capable CDN, or upload via browser / SFTP instead.
4. No admin setting enables IPv6 remote fetch today.