The alarm should go off when any fuel tank gets into the red. As mentioned in the alarm section of the manual, alarms are always tied to the red threshold. Sorry if we didn't make this obvious in the previous posts. The only "separate setting" is if there is an alarm at all, not the threshold for the alarm.
We've got thousands of EMS units in the field, and I've personally been in airplanes with the fuel level alarm going off, so let's figure this out. The alarm does work.
What software version are you running? Never heard of this as a bug, but let's start there.
Second, when we talk about "alarm," there are three of them in the EMS. First is a red bar that shows up on the screen. Second is an output on the EMS that can light an external light. Third is an audio alarm that can be run to an intercom system. Are you getting any of these? Which one are you expecting? If it's anything but the internal alarm bar, let's check the output first. There are output test functions inside the EMS.
Maybe this is something you should check on the ground when it's easier to play around with. You could take your airplane with X amount of fuel on board, set the red alarm to just below that amount, and then drain a small amount of fuel, or maybe just tilt the aircraft if that works for your design.
Also, feel free to give us a call at 425-402-0433 someday when you are out at your plane and we can try and troubleshoot it that way.