My settings for "Sight" in the campaign is
Maybe this is the problem? What is a good setting for this in 4E?
There is no good setting in 4e.
The problem is that maptool currently only has two states for light.
"Lit up" and "Dark". You can emulate shadowy or dim light by setting a color overlay for a light source, but as far as MT is concerned, something is either lit or not.
Lowlight in 4e does not let you see in the dark (that's Darkvision, obviously). All it does it make it so that dim light counts the same as bright light for those characters. However, they still need some light (dim) to see by.
The catch is that in dim light, both normal and lowlight characters can see things! The difference is not in what can be seen, or how far you can see, it's in how WELL you can see.
To normal vision, a target in dim light is VISIBLE, but also has partial concealment. The partial concealment is a matter of rules (-2 to hit, can use Stealth). Lowlight vision simply gets rid of that partial concealment.
But for the part that Maptool handles ("can I see this guy or not?"), dim and bright light are identical for ALL characters.
If EVERYONE in the group has lowlight, and the area you're in has dim (but overall everywhere) illumination, just set the vision mode to "Day" - this makes everything lit up, but still counts topology for FOW and LOS. If set to Night, you will need light sources.