Addons cannot be installed from an IPv6-only environment.
$ host -t AAAA addons.mozilla.org
addons.mozilla.org is an alias for olympia.prod.mozaws.net.
$ host -t AAAA olympia.prod.mozaws.net
olympia.prod.mozaws.net has no AAAA record
This requires access to a legacy IP environment to install addons.
Please add IPv6 support to addons.mozilla.org to remedy this situation.
Yes, ultimately all Mozilla web properties should be IPv6 enabled, but I thought I’d start with one place that I encountered a problem and hopefully work from there.