Why can't I vector paint this face?

I have had no trouble vertex painting the other side of this shop roof, but this piece to the right will not color. I have been trying and searching up what is wrong for 2 hours now but I can’t find anything. Here is a photo of the issue:

The area is highlighted I just can’t color it.

Hi @Henry3

Looks like you have a flipped face or double faces there, try tapping M, for merge by distance to merge faces, and ALT+ N to flip normals.

image

How would I merge it? At center, at cursor, or at collapse?

No, by distance like I showed in the first image.

https://duckduckgo.com/?q=flipped+normals+double+vertices+blender&t=chromentp&iax=videos&ia=videos&iai=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DNspb26j3Jq0

I suggest you watch this

This one too.