How to display multiple rects simultaneously

I am using MATLAB R2020a Psychtoolbox on Mac OS. I am trying to display multiple rects using the following code but can't seem to get it to work.

% Make a base Rect of 200 by 200 pixels
baseRect = [0 0 300 75];

% Pen width for the frames
penWidthPixels = 6;

% Screen X positions of our three rectangles
squareXpos = [leftX rightX upX];
squareYpos = [leftY rightY upY];
numSquares = 3;

% Make our rectangle coordinates
allRects = nan(4, 3);
for i = 1:numSquares
    allRects(:, i) = CenterRectOnPointd(baseRect, squareXpos(i), screenYpos(i));
end

%Draw rects to screen
Screen('FrameRect', window, allColors, allRects, penWidthPixels);