Solid Layer Unaffected by Curves

You didn't add your screenshot using the toolbar to embed it in the post so I had to download it and I see a lot of problems:

The biggest problems start with duplicating the mask, setting the bottom copy to subtract, and then making it smaller to reveal a white ring, then adjusting the subtraction mask's feather property to give the inside of the ring a soft edge. Start by fixing the problem by clicking the solo switch to isolate the layer, press m m to reveal all mask properties, delete mask 2, press Ctrl/Cmnd + D to duplicate Mask 1, set the bottom mask to subtract, if you need to press mm again to reveal all mask properties and reduce mask expansion enough so you can see a prominent white circle, then adjust the subtraction mask feather to soften the inside edge. 

When you get something like this you can add a blur to soften the outside edge. Once you have that done turn on all the other layers, verify that all the Glow layers have blur applied and that the blend mode is set to screen. I've not set the blend mode to screen on all of the glow layers yet. 

When you get that far you should see your Sun Sphere layer with a soft white glow. If you can get that far then adding an adjustment layer will allow you to change the colors of everything. You should be on your way. As long as you are using the Classic 3D rendering option Effects will work on the 3D layers and you will be able to see the blur that acts like a glow. 

If you have a solid that has 100% saturation (value) in one or more color channels and any of the others are at zero then bending the curve isn't going to change anything in the image because there are no intermediate values to manipulate. 

Andrew's tutorials are usually pretty thorough. If you are following the tutorial precisely and you pay attention to the settings for every new layer that is added to the comp and the colors used for any solids, things should work. If you can't figure it out we need to see a screenshot of your comp with the modified properties of the layer you are having problems revealed. Select the layer, press 'uu', and take a screenshot to show us everything changed on the layer. To diagnose the problem yourself start by soloing the layers you are having problems with, add one layer at a time until the trouble pops up, and then start turning off effects or resetting values. One more time, if you have solids or shape layers that are 100% red, green, blue, white, or black, bending the center of the Curves effect will do nothing to those layers. You have to have some color values that are not all the way up or down to have a change in the curve to make any difference in the layer's color.