Async custom function not working in office 365 PC

I use this sample code from office add in documentation to run async function

async function getStarCount(userName, repoName) {
  try {
    //You can change this URL to any web request you want to work with.
    const url = "https://api.github.com/repos/" + userName + "/" + repoName;
    const response = await fetch(url);
    //Expect that status code is in 200-299 range
    if (!response.ok) {
      throw new Error(response.statusText)
    }
      const jsonResponse = await response.json();
      return jsonResponse.watchers_count;
  }
  catch (error) {
    return error;
  }
}

It works in office 365 online in Chrome and Edge, but in Office 365 desktop version, it returns "#BUSY!" error.

Also, this is the log from OfficeAddins.log.txt runtime logging file

8/19/2020 15:05:08 Verbose Runtime [Console] [Log] Verbose CustomFunctions [Execution] [Begin] Function=STARCOUNT 8/19/2020 15:05:08 Verbose Runtime [Console] [Log] Host may not have set any promise continuation callback. Promises may not be executed.