Hello,
I unfortunately can't reliably reproduce this yet, but on the web client, from time to time I face the situation where the game panel i.e. the board or the card list just disappears, I can see the history text field followed right away by the action panel, but nothing between, while there should be the game panel.
There are various solutions to this problem. Sometimes just opening a menu from the action panel and returning back helps. Switching tables also works sometimes.
Though, there are situations when I need to restart the client to get this working again.
Before considering this a bug, I wonder, could there be some shortcut I'm not aware of hiding the game panel that I might be accidentally pressing?

Hello,
as far as I am aware, no such shortcut exists.

However, this is a long time bug I am facing as well. Today I have tried to find a reliable way to reproduce it, and I think I succeeded, at least on my side. I hope this may be enough for Aminiel to reproduce it on his side and try to see what is going on:

1. Open the web client and play a game of Scopa. It seems like it is important to finish at least one round. In case it matters, I reproduced this on both Classic and Scopone. So, play with a bot, and make sure to finish the round, or the entire game, this seems to work as well.
2. In the pause between the rounds or after the game is over, the game toolbar should still be here and working, but it will of course be empty.
3. Leave this table with Q and make any other table. In case that also matters, I reproduced it with both 1000 Miles and Yahtzee, so I assume it works with anything.
4. Once you are on this table, at least for me, the game toolbar has now completely disappeared. In the tab order, we have the history, followed by the actions toolbar, as you described.

The good solution is that the web client allows you to perform most shortcuts even from the history edit box. This means that if you go to the history and press Q, you will leave this table and the toolbar will appear again.
The bad side is that as soon as the list the server returns is again empty, for example by making a new table, the toolbar will again disappear. This seems to stay broken like this until you restart the web client.

Note: this is just one trigger. I have encountered this multiple times, and it always seemed to be related to the game finishing, and me doing something else after that, so there might be multiple causes for this error.

@Nikola awesome, fully reproducible on my side.