Extrange Behaviour with 2D Lights in Universal RP

Hello everyone,

I've created a 2019.3 unity 2d project, imported Universal Render Pipeline and created the pipeline asset and the 2D Renderer. I'va also updated the project to the new renderer. If I use a built-in sprite, like Knob, 2D lights work fine, but if I import one, lights behave badly.

I have imported a white and a green Sprite (1st image), but if I create a 2D point light, none of them is lit. The extrange thing is that, if I tweak the light color, there is a moment in whick the green square suddenly turns blue for a range of colors, and then green again, while the white never changes behaviour (image 2).

How can I make lights work properly?

Thanks.

Image 1:

Image 2: