Does it happen with any other application?
Also, are you using a wacom tablet?
Have you tried doing a clean re-installation of Photoshop using the Creative Cloud cleaner tool? Use the Creative Cloud Cleaner Tool to solve installation problems
I think I know what is happening. I have a track pad, and a Wacom Tablet. If I use the trackpad in another application and then come back to Photoshop to use my wacom tablet, the lasso and drawing doesn't work, but then it does work with the trackpad, and then after I use the track pad in Photoshop, the Wacom works again. Solution so far, when I see this issue, reengage the trackpad in photoshop, and in this way I don't have to restart Photoshop to fix the issue.
So, maybe this isn't a photoshop error, but a Wacom or Apple error? I'm not sure.