I should mention this already happened once, and fixed itself after a few minutes.
No longer able to increase board size

It has been since the dawn of time - nothing changed during the time this phenomenon appeared. One day the button was there, the next it wasn't.

Randomly, it seems, when I enter Play, the option to increase the board size (not the manual dragging one) is simply not there. Normally there would be 4 or 5 buttons, I can't remember, at the top right of the board whenever I enter Play. Now, there are only two, the settings icon and the flip board icon, and the button which looks like a "full-screen" button is no longer there, which forced me to play on a much smaller board (which I will not be doing). Is this a glitch or some permanent decision that removes my ability to change board size?
If the window size is too small, the Focus mode option doesn't show. Some other members have had to set zoom to 90% to get it to show.
If you can't see it and don't want to change your zoom, hit Z on the keyboard to enable/disable it

Hi Martin, I understand the zoom could be a potential issue, but I don’t think it is given I haven’t manipulated my zoom/screen size in an eternity. I am also familiar with the “z” shortcut, but that does not work for me either. Like I said, it was perfectly fine one day and the next it was like this. Could it be anything else?

Hi Martin, I understand the zoom could be a potential issue, but I don’t think it is given I haven’t manipulated my zoom/screen size in an eternity. I am also familiar with the “z” shortcut, but that does not work for me either. Like I said, it was perfectly fine one day and the next it was like this. Could it be anything else?
The option doesn't show if the screen/canvas isn't at least a specific size. It's possible that minimum size was slightly changed on the site definition and your screen now falls below that threshold.

I reduced my zoom to 90% for this site and the option returned, so thanks for the help. But I am wondering what the benefit is in this new requirement, it just seems unnecessary.

I reduced my zoom to 90% for this site and the option returned, so thanks for the help. But I am wondering what the benefit is in this new requirement, it just seems unnecessary.
Apparently there was an issue if the window/canvas size was smaller and they showed those icons. I don't know the specific problem, but I believe it had a layout problem of some sort and just not showing it when the size was too small was the fix.
Randomly, it seems, when I enter Play, the option to increase the board size (not the manual dragging one) is simply not there. Normally there would be 4 or 5 buttons, I can't remember, at the top right of the board whenever I enter Play. Now, there are only two, the settings icon and the flip board icon, and the button which looks like a "full-screen" button is no longer there, which forced me to play on a much smaller board (which I will not be doing). Is this a glitch or some permanent decision that removes my ability to change board size?