Boolean of object in simple cylinder

Hi Pros !

I try to subtract an object inside a cylinder for printing a negative mould.
I use 2.92 version.

I think that my inside objet is clean.

More than 2 days trying and i need help.

Thanks community !

Can’t upload (new user)
When was a old user ?

Check your normals. In edit mode, deselect all and hit Control N. Do it for both of your objects before trying the Boolean operation.