Can I get help?

Illustrator used to create vector halftones, it would be a great tool if the geniuses brought it back.  Otherwise, it will require a third-party plug-in to achieve.  The gradient is set to "radial" to add to the illusion of roundness.  My 1-bit halftone is something that possibly could be traced, thereby converting it ( the file ) back to vector.

The easiest and most clean way to create vector halftone effects like that in Adobe Illustrator is by using Astute Graphics' Phantasm plugin.

That is actually a radial gradient.  Not sure what size you are working at, but my approach is a little old school.  In Illustrator, create a circle, say 2.5" in diameter.  For your fill, use the radial gradient using black & white.  Set the black for approximately 80-85%, the white to around 20%.  Use the gradient tool to adjust the fill to go the way it appears in your sample ( sorry, offline so cannot show you screenshots ).  Open the gradient in Photoshop at 150ppi grayscale.  Use image > convert > 1-bit > halftone > shape = round > frequency around 25 LPi ( lines per inch ) > save as .tif > place in Illustrator and paint it purple over a light purple circle 2.5".  

First lets confirm am understanding your question correctly.

Looks to me like you are desiring to fil the dots group with a gradient from light purple to dark purple, but instead are getting all the dots filed with dark purple. That does not match the example on left where the dot size varies more to give the idea of a gradient getting darker at the top right.

I would remove all groups and fiulss adn mask. Then make a group of teh dots filed with none. Add a gradient at the group level. Wil be much quicker as your computer having a gradietn annotator for each dot will slow your computer.

Photoshop creates those rasterdots.