I have the following problem, I am setting up an application in Vue and I have a component from which I must upload files to my gcp bucket, but when it comes to sending the upload request from my front to the back, it gives me the error of the title
this is my front:

   <template>
      <div class="upload-container">
        <h4>Subida de Ficheros</h4>
        <b-form-file v-model="file" class="mt-3" plain></b-form-file>
        <button type="button" class="btn btn-primary" @click="uploadFile">Upload File</button>
        <p v-if="errorMessage" class="error">{{ errorMessage }}</p>
        <p v-if="successMessage" class="success">{{ successMessage }}</p>
      </div>
    </template>
    <script>
    import { sp } from '@/utils/constants'
    export default {
      data () {
        return {
          file: null,
          errorMessage: null,
          successMessage: null
        }
      },
      methods: {
        async uploadFile () {
          if (!this.file) {
            this.errorMessage = 'Please select a file to upload.'
            return
          }
          this.errorMessage = null
          const formData = new FormData()
          formData.append('file', this.file)
          try {
            const response = await fetch(sp + 'upload_file', {
              method: 'POST',
              body: formData
            })
            if (!response.ok) {
              throw new Error(`Error: ${response.statusText}`)
            }
            const result = await response.json()
            this.successMessage = 'File uploaded successfully'
            console.log('Response from server:', result)
          } catch (error) {
            this.errorMessage = `Error uploading file: ${error.message}`
            console.error('Error uploading file:', error)
          }
        }
      }
    }
    </script>
    <style>
    .error {
      color: red;
    }
    .success {
      color: green;
    }
    </style>

y este es mi back, montado en python del cual parece que aun no se ejecuta nada:

@surveys_bp.route('/upload_file', methods=['POST'])
    def upload_file():
        try:
            logging.info('Handling upload file request')
            if 'file' not in request.files:
                logging.error('No file part in the request')
                return jsonify({'message': 'No file part in the request'}), 400
            file = request.files['file']
            if file.filename == '':
                logging.error('No selected file')
                return jsonify({'message': 'No selected file'}), 400
            filename = secure_filename(file.filename)
            logging.info(f'File received: {filename}')
            # Intentar subir el archivo a GCP
            try:
                upload_to_gcp(file, filename)
            except Exception as e:
                logging.error('Error uploading file to GCP', exc_info=True)
                return jsonify({'message': f'Error uploading file to GCP: {str(e)}'}), 500
            logging.info('File uploaded successfully')
            return jsonify({'message': 'File uploaded successfully'}), 200
        except Exception as e:
            logging.error('Error handling upload file request', exc_info=True)
            return jsonify({'message': str(e)}), 500
    
    
    def upload_to_gcp(file, filename):
        """Sube un archivo a Google Cloud Storage."""
        client = storage.Client()
        bucket = client.bucket('files_pending_processing')
        blob = bucket.blob(filename)
        file_content = file.read()
        blob.upload_from_string(file_content, content_type=file.mimetype)
        logging.info(f'File {filename} uploaded to GCP bucket.')

The call never enters the back process, but always returns the error mentioned in the title.

I have tried sending the request with axios and now with fetch and nothing, it always indicates the same message and I have also included the content/type many times in the headers and nothing.