Cannot send file to room (server isolated from Internet)

### Steps to reproduce

1. Matrix-synapse installed from recommended package on Ubuntu 11. Server placed in isolated LAN without Internet connection. Internal DNS configured and workable
2. Element client allows me to register my username and password. I am able to chat, sent emoji, make audio and video calls.
3. I cannot post any file to the room from Android client. It shows, that file uploading in a progress but never finished.
4. From windows Element client I am able to post files to the same room.

### Outcome

Should be possible to post files to the room from Android

### Your phone model

Samsung A54 5G

### Operating system version

Android 13

### Application version and app store

1.6.3 (40106032)

### Homeserver

matrix-synapse-py3/unknown,now 1.86.0+bullseye1 amd64

### Will you send logs?

No

### Are you willing to provide a PR?

Yes