Does anyone else have this problem? As the title suggests, I am not getting any weapon debris from the patch.

I've gone into options and tried all the different settings for it, none of them work. Any advice would be greatly appreciated.

define 'weapon debris'

The 1.3 patch adds a new graphical effect for PC users, now various things (mostly bullet impacts) will create new particle effects based on whatever's being shot. The cool thing about these particles is that they won't fade away instantly and they'll respond to physics; https://youtu.be/wXLxp98TUxc?t=31s. It apparently uses an Nvidia-specific thing called FleX (or was it FluX), so only Nvidia cards get the effect unfortunately.

And I have an Nvidia card but still no effect. Is there perhaps another way of enabling it?

Hmm. Is the setting switching back to disabled each time you load up the launcher? Have you been making any .ini tweaks and then setting it to read-only? You could try deleting the .ini files in your My Games/Fallout4 folder - the launcher will create new ones if there aren't any there.

Tried deleting the file, no change. So sad...