How do i fix th brush tool

Continuing the discussion from Brush tool is not working:

There something wrong with the brush tool, I was in the middle of drawing something and for some reason the brush would stop working.it was a 100% Opacity, and the size was 10.00 px. I would restart krita and my computer and still nothing worked. I have the latest version of krita, and I use a Wacom Cintiq 16, and have windows 10. I would be so grateful if someone would help me how to fix this.

Check whether you have a selection active. Selections are saved in the .kra document.