Fresh web session is silently neither syncing nor sending messages

### Steps to reproduce

- Logged in (initial sync took 20 minutes)
- verified my session
- joined a room I had been invited to - read some of the scrollback, tried to send some messages
- messages stuck at "encrypting"; no new state has synced

### Outcome

#### What did you expect?

#### What happened instead?
as described above

### Operating system

Windows 10

### Browser information

Firefox 122.0 (64-bit)

### URL for webapp

app.element.io

### Application version

Element version: 1.11.55 Crypto version: Olm 3.2.15

### Homeserver

lant.uk

### Will you send logs?

Yes