Neural Filters, Colorize, no focal point

You are moving the slider to the On position?Do you see the black spot encircled in white, the "color focal point"?

(as an aside, is the Auto Color checkbox checked?)

No sarcasm intended.

I see the dot when I click in my image in the Colorize panel, and I see color added in the image on the left.

adding a question: is your image color or b/w? Have you selected a (color) Profile?