I cannot send encrypted messages to matrix.org, but I can receive them?!?

[Dominion0815]

Description

On my home server, I can send and receive encrypted messages to and from different servers without any problems.

But I cannot send messages to matrix.org, receiving them works fine. There is also no write notification when sending.

I also switched the Docker Synapse Worker setup back to Monolith for testing, but this did not bring any improvement.

I cannot find anything in the logs that directly indicates an encryption problem.

Is there anything else I can do to provide usable logs?

Steps to reproduce

I have no idea, from my other home server I can send and receive encrypted messages to matrix.org without any problems.

Homeserver

nope.chat

Synapse Version

1.104.0

Installation Method

Docker (matrixdotorg/synapse)

Database

PostgreSQL 14

Workers

Multiple workers

Platform

Debian 12.5 Docker Engine - Community Version: 26.0.1 Docker Compose version v2.26.1

Configuration

No response

Relevant log output

federation_transaction_transmission_loop-57 - TX [matrix.org] Failed to send transaction: Failed to send request: HttpResponseException: 520:

federation-reader-1-1  | 2024-04-14 13:31:27,645 - synapse.handlers.federation_event - 1621 - WARNING - _process_incoming_pdus_in_room_inner-204-$vFLgCEA_PHgyeB0Ena99jA2Ko2N2WtVKaN4f3RnTgTc-$IN2XvsDIUNwbE83Fd1oR6LWIjkh8_wrRppDcRMipeCk-$KPepzUH_IZuJcbnK3vkHmgixAundmJb4z80hUNGzhDQ-$2Lbm1lJsspYohzd6bVsBOm0BqMNgqvg7tmvuEbx1cWg - Server matrix.org didn't return event $2Lbm1lJsspYohzd6bVsBOm0BqMNgqvg7tmvuEbx1cWg

Anything else that would be useful to know?

No response