I’m trying to implement post processing effects in OpenGL by drawing a quad ( 2 tri) texture that replicates the screen but it is using the wrong shader

I’m not very experienced with OpenGL but I think glUseProgram() makes the window use the shader program of input but it doesn’t work. I’m using this guy’s tutorial: https://www.youtube.com/watch?v=atp3bzebWJE&t=561s and I’m pretty sure the error is somewhere in the render loop

code:

   while(!glfwWindowShouldClose(window))
   {

       glUseProgram(defaultShader.program);  // uses the normal shader
       glBindFramebuffer(GL_DRAW_FRAMEBUFFER, framebuffer);
   

       glClearColor(0, 0, 0, 1);
       glClear(GL_COLOR_BUFFER_BIT);

       
       glBindVertexArray(VAO.buffer); // VAO is for a test triangle
     
       glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_INT,0); // drawing test triangle

       glBindVertexArray(0);
       glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
    

       glClearColor(0.4, 0.8, 1, 1);
       glClear(GL_COLOR_BUFFER_BIT);

      glUseProgram(frameShader.program); // framebuffer shader
       glBindVertexArray(quadVAO); // the quad's VAO uses x y and texturec ooordinates
       glUniform1i(glGetUniformLocation(frameShader.program, "screenTexture"), textureColorbuffer); // not explicitly said in tutorialbut probably needed for the uniform^^^^

       glBindTexture(GL_TEXTURE_2D, textureColorbuffer);
       glDrawArrays(GL_TRIANGLES, 0, 3);

       glfwSwapBuffers(window);
       glfwPollEvents();

   }