Sometimes Element gives "Some of your messages have not been sent" with no clear way to fix it

### Steps to reproduce

No obvious steps to reproduce

### Outcome

It would be good if Element could give more detail about why the messages can't be sent. i.e. "They can't be sent because there's no internet connection or a different reason."

In this particular case my coworker could send messages to a different coworker but not to me.

### Operating system

_No response_

### Application version

_No response_

### How did you install the app?

_No response_

### Homeserver

mozilla.org

### Will you send logs?

No

Start by reproducing the failed message-send state in Element Web and trace the UI that displays "Some of your messages have not been sent." Determine which failure details are available when a coworker can message another recipient but not this one. Done means the interface explains the relevant reason or next step instead of showing only the generic warning.

Written by the indexing model from the issue text.