Stamper Tool Not Working

I normally use the stamper tool to place water, but now it won’t let me place anything, at all. I closed studio and reopened it and it still doesn’t work.

The gear/tool in Play Solo, or the actual Studio tool?

Studio tool

This is happening to me as well. It’s infuriating.

Mine too.
I can place blocks with the other tools, but not the Stamper.