Fluid Brush sometimes works, most of the time it doesn't respond

I haven't used Animate for years, so finding out there is now a fluid brush was great for me, since the brushes have always been a disaster in this program.

But, of course, it just doesn't work right away. It sometimes works. When I tap with my pen a couple of times it can sometimes draw a line. All other times it doesn't. 

Thinkpad with Wacom pen. Drawing for years on programs which are not Animate works great. Once I decide to use Aimate again, years later after the last time - brush problems again. Incredible.