Ok, @Micka understood. Commenting the resizing code helped check the mask image.
Finding ways to get the masked image working for contour detection. Current error:
cv2.error: OpenCV(4.5.4) :-1: error: (-5:Bad argument) in function 'findContours'
> Overload resolution failed:
> - image data type = 0 is not supported
> - Expected Ptr<cv::UMat> for argument 'image'
Edit: Resolved. This was a data type issue.