Saved MediaPipe Video isn't opening

Question

I am trying to save my video generated with landmarks and I get no error in my terminal and it actually gets save in my computer. However when I try to open it, I can'T open it. I get the following error:

Playback not possible The file cannot be played. The file format may not be supported, the file extension may be incorrect, or the file may be corrupted. 0xc10100be

Wiedergabe nicht möglich (Original: German language) Die Datei kann nicht wiedergegeben werden. Das Dateiformat wird möglicherweise nicht unterstützt, die Dateierweiterung ist möglicherweise falsch oder die Datei ist beschädigt. 0xc10100be

This is my code (I am using spyder):

import cv2
import mediapipe as mp
import numpy as np #for saving


mp_drawing = mp.solutions.drawing_utils
mp_drawing_styles = mp.solutions.drawing_styles
mp_pose = mp.solutions.pose

# Video Input (Replace 'your_video_file.mp4' with your video file path)
#cap = cv2.VideoCapture('Video_Reemt_Arm_1.mp4')
cap = cv2.VideoCapture('Reemt_Arms.mp4')
#cap = cv2.VideoCapture('Reemt_Feet.mp4')
#cap = cv2.VideoCapture('Reemt_Atmen_PTK.mp4') #dificil de detectar, intenta reconocimiento facial!
             
#cap = cv2.VideoCapture('Sam_Feet.mp4')
#cap = cv2.VideoCapture('Sam_Body.mp4')
#cap = cv2.VideoCapture('Sam_Atmen.mp4')

width = 600
height = 550

# Set the output video file name and parameters
output_file = 'output_video_with_pose.mp4'
fourcc = cv2.VideoWriter_fourcc(*'mp4v')  # Specify the codec (other options include 'XVID', 'MJPG', etc.)
out = cv2.VideoWriter('output_video.mp4', fourcc, 30.0, (width, height))

# Resizable window
cv2.namedWindow('Media Pipe Pose Estimation', cv2.WINDOW_NORMAL)

with mp_pose.Pose(
        min_detection_confidence=0.5,
        min_tracking_confidence=0.5) as pose:
    while cap.isOpened():
        success, image = cap.read()
        if not success:
            print("End of video")
            break

        # Drawing
        image.flags.writeable = False
        image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
        results = pose.process(image)

        image.flags.writeable = True
        image = cv2.cvtColor(image, cv2.COLOR_RGB2BGR)

        mp_drawing.draw_landmarks(
            image,
            results.pose_landmarks,
            mp_pose.POSE_CONNECTIONS,
            landmark_drawing_spec=mp_drawing_styles.get_default_pose_landmarks_style()
        )

        # Resize the window to match the video frame size
        cv2.resizeWindow('Media Pipe Pose Estimation', width, height)
        cv2.imshow('Media Pipe Pose Estimation', image)
        out.write(image)
        
        if cv2.waitKey(1) & 0xFF == 27:
            break

cap.release()
out.release() 
cv2.destroyAllWindows()

I've already try:

1. saving it with another VideoWriter like XVID, 'MJPG'or 'H264' eg.:

fourcc = cv2.VideoWriter_fourcc(*'XVID')
output_file = 'output_video_with_pose.avi'  # Use .avi extension
out = cv2.VideoWriter(output_file, fourcc, 30.0, (width, height))

2)Updating OpenCV

3)Using different media player

4)Checking my original video

5. Debugging

What I am doing wrong? Why can't I view my video?