generate thumbnails of mp4 files using fluent-ffmpeg on node.js

Question

I'm trying to generate thumbnail of mp4 video files on a node server and I'm using fluent-ffmpeg. My goal is to be able to send it to the frontend. I thought that I'm able to convert the video file but when I try to load and preview it on the frontend, nothing really shows up. Here is my code

   const ffmpegPath = require('@ffmpeg-installer/ffmpeg').path
   const ffmpeg = require('fluent-ffmpeg')
   ffmpeg.setFfmpegPath(ffmpegPath)

let thumbnail
const outputPath = `${url.replace('.mp4', '.png')}`
              await new Promise((resolve, reject) => {
                ffmpeg(url)
                  .seekInput('0:01')
                  .size('150x150')
                  .frames(1)
                  .output(outputPath)
                  .on('end', () => {
                    const thumbnailPath = outputPath
                    console.log(thumbnailPath, 'thumbnailPath')
                    resolve(thumbnailPath)
                  })
                  .on('error', error => {
                    console.error('Error generating thumbnail', error)
                    reject(error)
                  })
                  .run()
              })
                .then(thumbnailPath => {
                  thumbnail = thumbnailPath
                  console.log(thumbnail, 'thumbnail')
                })
                .catch(error => {
                  console.error('Error generating thumbnail:', error)
                  Sentry.captureException(error)
                })
            }

The output of this is:

'https://sample.nyc3.digitaloceanspaces.com/uploads/300705/1899672-sample-file.png'

and this is what is being received on the frontend.

Anybody have any tips to fix this? Not sure what it's going wrong here. Thank you!