To get a download you will need software to talk to it. Unless your vendor gave you a copy it will not be easy to get and several versions were built so you need the right one.
The real issue is the battery it holds everything in memory if it is unplugged too long and the battery dies you have a defaulted system.... nothing will work. The battery might hold up for hours but it might hold up for 30 seconds and it's all gone before you can get it back up.
You really need to get your vendor involved, if that just isn't an option replace the battery and hope for the best. The battery needs to be swapped HOT. If you power the system down and take it out your defaulted. Remove the side panel with it running and pull the black clip, it has tabs on both ends after you get it off you can pull the battery out.... I did a search to find an outlet for the battery this is what I found
https://www.batteriesandbutter.com/...ct_Code=TL-2150S&Category_Code=sa36v This really might be a good time to look at an upgrade... you can buy a controller and reuse your phones and you would get a TON of features you don't have now
Randy
Randy