"Join meeting" button in pre-meeting screen not clickable.

### Steps to reproduce

Element-desktop 1.9.8 and Element-nightly 2022011301 under Debian 11.2/stable
with KDE/Plasma, with a local private matrix-synapse 1.49.0-1~bpo11+2 server,
also under Debian 11.2 with backports.

Some of the symptoms are the same as described in

https://github.com/vector-im/element-web/issues/18506

like the disconnections every 30 seconds.

Description

On startup, the main window pops up and displays the text messages just fine.
When I click on the jitsi icon the video field displays "Jitsi Video
Conference" and a button to "Join Conference".

When I do that, the video screen shows the camera input and at the bottom
half of it the pre-meeting screen has a white field with my user name and
a blue button to "Join meeting". Clicking on this button has no effect. I
can never join the meeting.

Shortly after (30 seconds), a pop-up says "You have been disconnected, you
may want to check the network connection. Reconnecting in 30 seconds." and
then it counts down. Then it disconnects again and again. This is the
same symptom described in issue 18506.

This goes on until I exit the program or I disable the pre-meeting screen
from the settings gear on the pre-meeting screen. If I do the latter I
see a grey screen with my camera input in the corner greyed out until the
next disconnection. At that time, the corner mini-screen goes black (with
the AV circle on it and the microphone and camera icons slashed out.
Clicking on the microphone or camera icons that show up when you move the
mouse over the video field don't enable them. The only thing that works
is the red hang-up button, which brings me back to the "Jitsi Video
Conference with the "Join Conference" green button" field.

Reconnecting now goes directly to the grey screen (no pre-meeting screen as
that has been disabled) until the next disconnection. The first time (before
the first disconnection, the field at the top (when mouse is hovering over the
video field had the name of the room, subsequent times it had "Jitsi Heb...".

At least I can access the config menu (...) and re-enable the pre-meeting
screen. When that is done, it's back to the unclickable blue "Join meeting"
button. However, now the microphone and camera icons in the pre-meeting
screen are usable. Clicking them re-enables the video in the top half of the
video screen.

So, it is totally impossible to make video calls from this system and the
sequences above are totally repeatable. What can I test or where can I look
to find more details to track down this issue? Some of this behavior has
been present for a few releases, before that Element-desktop worked
correctly on this computer, and most recently it did so a few days ago, until
apparently the latest upgrade. I do not remember upgrading element-desktop
manually but the pre-meeting screen is new, so I suspect this latest behavior
has been caused by the latest release.

On another computer (a laptop with built in camera) with the same debian
stable OS, I see the same issue with the pre-meeting screen but once that is
disabled, the video part of the screen turns grey and no amount of hovering
or clicking can bring up the red hang-up button, so it is impossible to do
anything but exit the program.

I have seen on a few occasions a very quickly disappearing pop-up message at
the beginning, when I just started the program, but it disappeared in less
than a second, so couldn't read what it said.

### Outcome

#### What did you expect?
That I could join the specified room via video call like I had done before.
#### What happened instead?
The program is totally unusable.

### Operating system

Debian 11.2/stable with KDE/Plasma, with a local private matrix-synapse 1.49.0-1~bpo11+2 server, also under Debian 11.2 with backports.

### Application version

Element-desktop 1.9.8 and Element-nightly 2022011301

### How did you install the app?

deb [signed-by=/usr/share/keyrings/riot-im-archive-keyring.gpg] https://packages.riot.im/debian/ bullseye main

### Homeserver

local private matrix-synapse 1.49.0-1~bpo11+2 server, also under Debian 11.2 with backports.

### Will you send logs?

Yes

Start by reproducing the pre-meeting failure on the Debian and Element versions reported, then compare the symptoms with issue 18506 and inspect the logs the reporter offered to provide. Done means the Join meeting button works, video calls can be joined, and the repeated disconnections and unusable controls no longer occur.

Written by the indexing model from the issue text.