Unable to decrypt message, keys aren't getting transferred from other devices

[TellowKrinkle]

Steps to reproduce

1. Sign into your account on a new device
2. Verify the session from an already signed in device
3. Try to view encrypted messages on the new device
4. According to https://joinmatrix.org/guide/fix-decryption-error/, if you view the same messages on a device that has the keys, they will be transferred to the new device in a "few moments"

Outcome

What did you expect?

The messages will be decrypted in less than a minute

What happened instead?

Still shows unable to decrypt message after multiple minutes

Operating system

Fedora Linux

Browser information

Firefox 127.0

URL for webapp

app.element.io

Application version

Element version 1.11.69, Crypto version Rust SDK 0.7.0 (068a0af), Vodozemac 0.6.0

Homeserver

matrix.org

Will you send logs?

Yes

[kegsay]

This is due to the other client (not the new one) not having the m.megolm_backup.v1 secret, but it has the other 3 (SSK, USK, MSK).

Confusingly, functions which get access to the backup key are producing different results:

• this code produces a truthy response, but
• this code produces None.

[jblachly]

I recently signed in with a new web browser. My existing mobile element session is not sending keys.
In contrast to the message in tchapgouv/tchap-web-v4#904 (referenced above), I instead have the following info (in "view source") for all the undecryptable messages:

{
  "type": "m.room.message",
  "content": {
    "msgtype": "m.bad.encrypted",
    "body": "** Unable to decrypt: DecryptionError: This message was sent before this device logged in, and key backup is not working. **"
  }
}

[richvdh]

I don't really know what's going on with this issue. It describes a particular user's failure mode, but no attempt appears to be being made to investigate it. There's not much point keeping issues like this open forever, waiting to confuse other users who come across superficially-similar symptoms but completely different causes.