To connect to a pad, both the track and the clearance around it has to fit in between the adjacent tracks. With your color settings, the light grey areas are the clearances between the pads and the tracks. These clearances can overlap with each other, but they may not overlap with copper from another net. And in your case it does not fit. You can change this in the board setup. The quickest way is probably to simply change the settings of the "Default" netclass, but overall, net classes are a quite nice and useful method to manage different track and clearance widths for different purposes and you should invest some time into what net classes are and how they work.