Rollback Harmony firmware if your Harmony stops responding to your home automation.

Seems Harmony Hub FW 4.15.206 has a bug in it that cause the the hub to no longer respond to API requests. The simplest way to fit this it to roll back the firmware. Here are the steps that work from a  reddit post.

1. Launch MyHarmony app on PC.
2. Press Alt+F9 to open the advanced tools menu
3. Scroll the window to find your Harmony model.
4. Select "Factory Reset" for the appropriate model. This does not do anything immediately.
5. Steps 1-4 will be displayed for completing a Factory Reset. We are only doing Step 1. "Restore" here means "Rollback".
6. Connect your Harmony hub to the PC via micro-USB.
7. Within a few minutes, it will be detected by MyHarmony and display Remote Model, Firmware Version, and Hardware revision. The Restore button will be enabled.
8. Click "Restore" and wait. (Now is the first time that it actually describes that it's a rollback!)
9. When it completes, you should be on Firmware Version 4.15.193. Disconnect the hub from the PC and return it to its original location.

You might want to block WAN traffic to and from your Harmony hubs till an update it posted.

Update:12/19

Next morning my main remote was not talking to the matching hub. Tried to sync it but it seems that required unblocking the hub from the internet.

Update: 9/1/2019

They have made turning on XXMP an option the the current firmware releases. Not sure how long this is going to last but the 2 Homeseer plugins both seem to still require XXMP to work. Note when I did this the option is at
Menu > Harmony Setup > Add/Edit Devices & Activities > Hub > Enable XMPP
not
Menu > Harmony Setup > Add/Edit Devices & Activities > Remote & Hub > Enable XMPP