Some users are reporting being unable to remove threepids from their homeserver or from vector.im identity server

[lampholder]

Clicking 'Remove' to remove the address from the homeserver causes:

Unpublishing from the identity server gets you:

I don't know which action causes it, and I don't know where it appears in the unbinding flow, but at some point vector.im is calling /key/v2/server on the homeserver and getting back an unexpected and unhandled 404:

Possibly related:

• Can't change username? element-hq/element-web#8927
• Deactivate Identity synapse#4028 (comment)

[dklimpel]

I had the same issue on my own sydent/synapse server.
My solution was to add the path to the federation vhost:

server {
    listen 8448 ssl;
    server_tokens off;

...

    location /_matrix/federation {
        proxy_pass http://localhost:8009/_matrix/federation;
        proxy_set_header X-Forwarded-For $remote_addr;
    }

    location /_matrix/key/v2/server {
        proxy_pass http://localhost:8009/_matrix/key/v2/server;
        proxy_set_header X-Forwarded-For $remote_addr;
    }
}

[jaywink]

The mentioned reports came from Modular hosts. We identified a routing problem related to hosts that are set to not federate and using the vector.im IS. The fix has been rolled out to all Modular hosts, so I'm closing this issue.

As mentioned by @dklimpel , the solution when running in not federated mode is to add the keys listener resource which is normally included in the federation listener resource - see https://github.com/matrix-org/synapse/blob/master/docs/sample_config.yaml#L172