Detecting all edges of PCB using houghs transform (Matlab)

Question

I am trying to write a code that will ultimately detect and plot the corners of a PCB as well as outline the two sides and top edge shown in the camera view. I am trying to do this using a Houghs Transform and line identification. I want to outline the three edges shown in the camera view ( two sides and top edge) and plot the intersections of the top line with the two side lines, marking the top two corners of my PCB. I Have a code that does a simple line detection based off MATHWORKs documentation. I will also share the original picture, as well as the edge detected picture and the lines overlayed on the original camera view. Can anyone explain why only the right edge is being detected, and steps i can take to ensure the other that the other two edges (top and left side) are to be detected and outlined as well? Original Test Image) Edge Outline Final Result with only right edge detected

clc; clear all; close all
%% Initialize Cameras
camList = webcamlist; % camera list, figure which is top view
cam = webcam(3);  
cam.Resolution='1280x960';
%% set parameters
filter=105; %Intensity of pixel to base filter on; originally at 100
line_num=3; 
fill_gap=200;
parameters=[filter,line_num,fill_gap]; % detection parameters
%% Take image
I2=snapshot(cam);
imshow(I2)
%% Turn image to grayscale
I0=rgb2gray(I2);
imshow(I0)
%% Index pixels that are lighter than filter value
index=find(I0<parameters(1));
%% Make Matrix of same size as original picture w/ all black
Ix=zeros(size(I0));
%% Paste pixels that passed filter onto the all black matrix
Ix(index)=I0(index);
imshow(Ix)
%% Detect Edges of newly created, whited out image
I3 = edge(Ix,'Roberts');
imshow(I3)
%% Houghs Transform
[H, theta, rho] = hough(I3)
P = houghpeaks(H,parameters(2),'threshold',ceil(0.7*max(H(:))));
%% plot peaks
imshow(H,[],'XData',theta,'YData',rho,'InitialMagnification','fit');
xlabel('\theta'), ylabel('\rho');
axis on, axis normal, hold on;
plot(theta(P(:,2)),rho(P(:,1)),'s','color','white');
%%
lines = houghlines(I3, theta, rho, P,'FillGap',parameters(3)); %info about the lines extracted
%%
figure, imshow(I2), hold on
for k = 1:length(lines)
   xy = [lines(k).point1; lines(k).point2];
   plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green');
   % Plot beginnings and ends of lines
   plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow');
   plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');
  
end

I am expecting all three edges to be overlayed so that i can plot their intersections and find the two top corners to the PCB. When i ran the above code, i only recieve line detection on the right side of the PCB. That line is almost perfect, i just need the top and left side to do the same. The third picture linked 'Final Result with only right edge' shows what i am refferring to.