Where on motion sensor is the battery on the 2550 bravo. I don’t see it When opened
I suspect there are multiple alarms and the readout on the panel controller is mashing the errors together and what you have is a SYSTEM BATTERY low plus another alarm such as one of the motion sensors is triggered so you are reading it as a motion sensor low battery.
According to the manual for the 2550 it powers the motion sensors from the panel there are no batteries in the sensors themselves.  The panel uses the standard lead acid Gel Cell.
Most of these alarm panels are very similar in how they work and most are designed to dial a telephone number to an alarm monitoring company that you pay a subscription to.  I assume you have one of those since a residential burglar alarm that sounds off in the middle of the day (even for a long time) is going to result in the neighbors ignoring it. Many of those panels allow remote service techs to dial into the panel, the usual procedure is the panel lets the phone ring 15 times or so then answers. (if it's programmed to do so)  Call your alarm monitoring company and see if they have a service department that can do this and if so their techs can pull the codes.
However before spending any time on this look at the lead acid gel cell in the panel.  If it is more than 3 years old, replace it.  If you can't tell how old it is replace it.  Make sure to date when the battery was replaced.