First off, have you completed the Glowforge tutorials?
In order for the Glowforge to cut or score, the lines must be vectors. It sounds like your file is a raster image (svg files can contain both vector and raster elements) or has filled vector shapes. Rasters can only be engraved, not cut or scored.
This post may be helpful to you: Glowforge Interface - Vector Files Made Easy 🤔