Please check the following settings.
- The “use pen pressure” setting is disabled.
- Palm rejection is disabled.
- You have not selected text layers.
- You are not using faint colors on bit layers.
- You did not accidentally select the Eraser tool.
- You are have not accidentally switched from the primary color or secondary color to the transparent color.
If after checking the above settings you still cannot make any marks on your canvas, please Contact Us.