Not sure what browser you're using but did you try it when you just had the SOS Forum open or when you were typing a reply in the little text box?

OK, try it this way.

See on your keyboard there is Ctrl button in far left front?

Put your finger on that and at the same time put another finger on the plus sign + which should be next to Backspace. Do it simultaneously.

Don't do it with the text window open, where you type a reply. Do it before you reply when you have a thread open or a main page open.

To decrease size, if you make it too large like I just did LOL, you just click Ctrl and the minus sign - In between the naught 0 and the equal sign = on your keyboard.