I recently updated the firmware on my Phantom 4 to V01.04.0602.  It is not working well with the app, Autopilot, and it has been suggested that I downgrade the firmware. I cannot figure out how to do this.

So far, I have tried using the DJI Assistant 2 v1.0.9, available on the downloads page, but when I connect the drone it states that I have the latest firmware and offers no options to download and install older firmware.

I also tried dowgrading the firmware in the app, by connecting DJI Go and holding the 3 little lines on the start screen as decribed here https://www.youtube.com/watch?v=6rf0elzz52g, however there is no option to download the older firmware to swap it out.

Is it possible to downgrade the firmware? Any help would be appreciated.

As far as I'm aware there is no downgrade path available now for the Phantom 4. I'm not familiar with Autopilot App', but if you have latest version then you could try reinstallation of App'. Also through Assistant 2 you could try a refresh and factory reset of firmware and P4 which may or may not help.

Yes, I tried the factory reset through Assistant 2 but it did not work. I have not yet resinatlled the app, as their website specidifcally states that there is a firmware issue and recommends the downgrade. I would think it must be possible.

Reference: https://autoflight.hangar.com/autopilot/flightschool

"We recently discovered an issue that may cause Autopilot to become unresponsive when first connecting to an aircraft. The root cause of this issue has not been identified, but it appears to be related to the recent firmware updates. You may downgrade your firmware to continue using Autopilot at this time.
Last Update: Jun 12, 2017 11:50:50 AM UTC"

I assume you have the Phantom 4 Pro, as the firmware you quoted is for the P4P.

It was an option at one time to downgrade the P4, this was removed at about the same time as the last update was introduced for the P4. I assume that the same applies to the P4P, if there is no option in Assistant 2 to roll back the firmware then that is it. Autopilot will have to wait for a fix from DJI, or find out why their software does not work with the latest build.