Timeout - Async call back not invoked when using jest.useFakeTimers('modern') and jest.setSystemTime()

I am trying to mock today's date using jests timing functions.

Previously, I was mocking out dayjs with the following mock:

jest.mock('dayjs', () => {
  const mockDayjs = (date = 'Fri Sep 25 2020'): dayjs.Dayjs => jest.requireActual('dayjs')(date);
  return mockDayjs;
});

It was suggested that I change this to use the out of the box jest functions as follows:

  beforeAll(() => {
    jest.useFakeTimers('modern');
    jest.setSystemTime(new Date('Fri Sep 25 2020'));
  });

  afterAll(() => {
    jest.useRealTimers();
  });

This worked for one unit test, but failed for another test with the following error:

● server: custom reports › post - success

    : Timeout - Async callback was not invoked within the 5000 ms timeout specified by jest.setTimeout.Timeout - Async callback was not invoked within the 5000 ms timeout specified by jest.setTimeout.Error:

The only main difference between the two tests is that the failing test is asynchronous. Wondering if I am missing something here. Thanks!