"we couldn't reach this homeserver" is incredibly vague and hard to debug

[anarcat]

Steps to reproduce

1. i'm trying to login to matrix.debian.social with element x
2. i follow the login process and enter the homeserver URL and fail

Outcome

What did you expect?

I expected to be able to login to the homeserver. It's running synapse 1.127.1 so it should have sliding sync (right?).

What happened instead?

Instead, it now fails on the MAS stuff, as it gets a 404 on /_matrix/client/unstable/org.matrix.msc2965/auth_metadata.

It seems to me this could be relayed back to the user. There are a couple of similar bug reports in this issue tracker, yet they all vary subtly:

• "We couldn't reach this homeserver" with a valid homeserver URL (without sliding sync support) #1097 is about missing sliding sync support (same error message!)
• I can't login to any homeserver at all: "We couldn't reach this homeserver" #3447 seems to be about proxy issues
• "We couldn't reach this homeserver." - Possible issue with SSO #954 is similarly unclear but seemed to be about SSO

In generaly, percolate back to the user the actual error, including the HTTP status code and the URL it tried to reach. Telling users to "contact their homeserver admin" is not really useful, especially when the user is the homeserver admin. I only found out what the issue was by connecting to a separate IP (so i could find the traffic in the log) and grepping homeserver.log, which is not really intuitive.

I am also, fundamentally, puzzled that Element X already requires MAS given that this was deployed only last week on Matrix.org. Maybe I'm missing something?

Your phone model

irrelevant

Operating system version

Android 15 / CalyxOS

Application version and app store

element x from f-droid

Homeserver

1.127.1

Will you send logs?

Yes

Are you willing to provide a PR?

No

[alexander-potemkin]

Same on iOS - spend a few days, have no glue how to troubleshoot it at all

[alexander-potemkin]

As it's turned out, it could also mean that the server accept TLS 1.3, which is not supported: element-hq/element-x-ios#786

[ShadowRZ]

@anarcat

I am also, fundamentally, puzzled that Element X already requires MAS given that this was deployed only last week on Matrix.org. Maybe I'm missing something?

Yes you missed something.

https://matrix.debian.social/_matrix/client/v3/login Looks like this:

{
  "flows": [
    {
      "type": "m.login.sso",
      "identity_providers": [
        {
          "id": "oidc",
          "name": "Salsa",
          "brand": "salsa"
        }
      ]
    },
    {
      "type": "m.login.token"
    },
    {
      "type": "m.login.application_service"
    }
  ]
}

However Element X Android only supports these two methods:

• Username / Password
• Next Gen Auth provided currently with matrix-authentication-service, this is different from the Synapse's builtin SSO

But besides this, yes Element X Android can't communicate with user that this homeserver had this kind of unsupported configuration.