ERROR event: Not Found; when triggering event from another event : probot app built in nodejs

I am building a GitHub app in probot and nodejs and trying to update the PR whenever a pull_request.synchronize event occurs. I know that doesn't make much sense, but the point is I want to be able to update the PR upon the occurrence of a certain event.

app.on('pull_request.synchronize', async context => {
    console.log('---------------------- on pull_request.synchronize, body of PR : ', context.payload.pull_request)
    console.log('State of PR after pull_request.synchronize event :---------------', context.payload.pull_request.state)
    await context.github.pulls.update({
      owner:context.payload.repository.owner,
      repo :context.payload.repository.name,
      pull_number :context.payload.pull_request.number,
      title:'updated Pull Request Title: Success',
      body:'updated Pull Request Body: Success',
    })

  })

I get below error every time :

    ERROR event: Not Found (id=ssjsk-dd-sdfsdfs-fsfs-fsfsfsffsd)
  HttpError: Not Found
      at response.text.then.message (C:\GitWorkspace\user\GitHubApps\github-app-name\node_modules\@octokit\request\dist-node\index.js:66:23)
      at process._tickCallback (internal/process/next_tick.js:68:7)
  --
  event: {
    "event": "pull_request.synchronize",
    "id": "2332-3131-131-31231313-1313232144142",
    "installation": 3352243,
    "repository": "user/Demo-Repo"
  }
06:24:58.460Z ERROR probot: Not Found
  HttpError: Not Found
      at response.text.then.message (C:\GitWorkspace\user\GitHubApps\github-app-name\node_modules\@octokit\request\dist-node\index.js:66:23)
      at process._tickCallback (internal/process/next_tick.js:68:7)
06:24:58.472Z  INFO http: POST / 500 - 519.93 ms (id=3424234-43242-42423478a-4242-42342342)
06:24:58.476Z ERROR probot: Internal Server Error
  Error: Internal Server Error
      at Request.callback (C:\GitWorkspace\user\GitHubApps\github-app-name\node_modules\superagent\lib\node\index.js:706:15)
      at IncomingMessage.parser (C:\GitWorkspace\user\GitHubApps\github-app-name\node_modules\superagent\lib\node\index.js:916:18)
      at IncomingMessage.emit (events.js:203:15)
      at IncomingMessage.EventEmitter.emit (domain.js:448:20)
      at endReadableNT (_stream_readable.js:1129:12)
      at process._tickCallback (internal/process/next_tick.js:63:19)

Why is it unable to get the detail out of context, when in fact the context does get printed out by my console statement and contains the pull_request details.

I am just a beginner in both probot and nodejs so I am not sure if this has anything to to do with the syntax.

The problem is that context.payload.repository.owner is an object, compare the example payload at https://developer.github.com/v3/activity/events/types/#webhook-payload-example-28

Try to replace it with context.payload.repository.owner.login.

Probot also provides a convenience method which returns and { owner, repo } object based on the context, and you can pass extra parameters to it

Try the following

await context.github.pulls.update(context.repo({
  pull_number: context.payload.pull_request.number,
  title:'updated Pull Request Title: Success',
  body:'updated Pull Request Body: Success',
}))