Cartoon Shaders on Display Regions

I just applied cartoon shaders to my project, but when I did so, one of my display regions disappears.

I tried this:

    #####################
    """Cartoon Shaders"""
    #####################
    def toonShaders(self):
	# Check video card capabilities.

        if (base.win.getGsg().getSupportsBasicShaders() == 0):
            addTitle("Toon Shader: Video driver reports that shaders are not supported.")
            return

        # Enable a 'light ramp' - this discretizes the lighting,
        # which is half of what makes a model look like a cartoon.
        # Light ramps only work if shader generation is enabled,
        # so we call 'setShaderAuto'.

        tempnode = NodePath(PandaNode("temp node"))
        tempnode.setAttrib(LightRampAttrib.makeSingleThreshold(0.5, 0.25))
        tempnode.setShaderAuto()
        self.my_camera3.node().setInitialState(tempnode.getState())
        self.my_camera1.node().setInitialState(tempnode.getState())
        
        # Use class 'CommonFilters' to enable a cartoon inking filter.
        # This can fail if the video card is not powerful enough, if so,
        # display an error and exit.

        self.separation = 0.01 # Pixels
        self.filter1 = CommonFilters(base.win, self.my_camera3)
        self.filter2 = CommonFilters(base.win, self.my_camera1)
        filterok1 = self.filter1.setCartoonInk(separation = self.separation)
        filterok2 = self.filter2.setCartoonInk(separation = self.separation)
        if (filterok1 == False):
            addTitle("Toon Shader: Video card not powerful enough to do image postprocessing")
            return

…but that doesn’t help.

I am thinking I should in some way link that display region to the main display region (self.my_camera3), but I am not sure how to do that.

Can someone help me with this please?

I’m sorry.
I misunderstood what was actually happening to my displayRegion and toonshaders. At first I thought that one of my displayRegions disappeared because I needed to set the toonshaders on it, but then I realized that I had other displayRegions about the same size that did not disappear. So what is the problem?

I would like to place an image to show what I mean, but I don’t know how to. So here is a description of what i mean:

I have 4 displayRegions. The main one (#3) covers most of the screen. Another (a small one #2) is at the top left. A similar size one (#4) is at the top right. Finally (#1) - the one that disappears is in the center.

I don’t understand why my center displayRegion disappear when I enable toonshaders? Can anyone help me with this?