Problem with line spacing in converted .epub files

Hi,

I've been encountering an issue with the files I'm converting from .docx to .epub using Calibre. When I try reading the output file on my Kobo, it shows up with a small line spacing, and I can't adjust it using the text options on my e-reader. Does anyone know how to resolve this issue?

I'm using a Kobo Aura ONE, if that's relevant.

Thanks in advance1