If it settles late, the reason is usually barbs. If it never settles, that's usually because it doesn't see any spots that reach a 'desirability' threshold. It's set up now so that it decreases that threshold when it builds more cities, so that it'll progressively allow itself to settle worse locations. This so that it can end settle that terrible tundra spot lategame, but not during its initial expansion.
Rarely that does mean it never gets through that initial hurdle if there's almost no good spots (both screenshots don't really show any spots available it would consider good). There's no good way for me to decrease the threshold based on game turns or something like that. I guess your 4 range thing does significantly reduce the amount of spots available, so that could make it more likely it ends up doing this.
I didn't change anything on this in v10 btw, have you been seeing this in v9 too?
Im planning on uploading it on the workshop, and will continue updating here too.