Acu-rite 00896 Digital Wireless Rain gauge problem?

Yes my parents had an Acu-rite Digital Wireless Rain Gauge just sitting in its package in the house for about a year or so. Hadn't been opened or used. I thought I would open it and set it up for them. I open it and do as the instructions tell me to do. Place batteries in the indoor receiver first, then put batteries in the outdoor receiver. It shows that it connect but the problem is. the low battery light on the outdoor receiver keeps blinking and they are brand new batteries. i tried different ones and the problem is the same. I know its an old rain gauge but does anyone know what is going on with this thing?? I have googled everywhere and found nothing to help considering its older. Help would be much appreciated.