Texturing an imported model - subset of the whole

[max72]

I have a survey of a small chapel, thar registered fine.
Of the same I created a simplified 3D mesh of a subset of the structure, in the same system coordinates.
I imported it in Metashape and I would like to be able to texturize it but I get messed up textures.
How should I proceed to texturize it?

I attach a couple of screenshots of the full photogrammetry model, and of the simplified model

Thanks in advance,
Massimo

[max72]

Short update:
I found the issue:
I had the normals flipped..

Massimo