Paint Brush Tool in Illustrator not working

Hi!  Trying to use the paint brush in Illustrator - it was working fine this morning, but came back to my project this afternoon and got the "circle/diagonal slash" symbol when attempting to use the brush.  I can use the pencil with no problem.  Any idea what I am doing wrong to get the paint brush tool blocked?  Thanks- Marilyn

You need to ask program questions in the forum for the program you are using
To ask in the forum for your program please start at https://community.adobe.com/
Moving from Using the Community (which is about the forums) to the correct forum... Mod