Don, you are going to have to give us a lot more info before we can help. What tool are you using? What are you trying to 'draw' on? Is it an image layer and not an adjustment layer? Is the layer locked? are you painting white on white, for instance? What blend modes are involved. Tablet or mouse?
You might as well add Photoshop version and operating system.
I'm trying to use a paint brush on a image layer already loaded with the file. Also added new layer with no luck. I'm using the latest cc version on windows. Layers were not locked. No blend modes and it is not working with a tablet or a mouse.
Could you post a screen shot with the layers panel open? It would be best to capture the entire screen.
Don the fact that you tried with a new layer, eliminates just about anything that I can think of. When you say no modes involved, are you just talking Layer modes, or have you also checked the brush mode? Some tutorials might ask you to put the brush into Overlay, for instance, when cleaning up an Alpha channel mask.
You also haven't made it clear if this is one particular image, or all images. If it is one image, then I am guess this one of those times when Photoshop gets its knickers in a twist. When that happens to me, I select those layers that I need, and either Group them, or turn into a Smart Object. Grouping is the most flexible. I then right click that group, and choose Duplicate Group. When the panel opens, I use the drop down to select New. I then carry on with the new document and delete the old one. That has never failed yet for me.
If it is all images, then time to get heavy handed, and reset the Preferences file by holding down Shift Ctrl Alt as you start Photoshop.
If you have a problem after that, then my guess is that you need to reinstall Photoshop.