We have an external battery backup but it runs out if the power's out for more than a few hours. There's a cartridge inside that says Backup and the red LED is blinking rapidly.

I tried changing all stations and trunks to 501 and next port 529 but the only thing that did was to stop the ringing when it forwards to 500 and gets stuck in a loop. I wish I could remember what I did to fix it the last time. I distinctly remember having to create a 500 mailbox through the VMADMIN button but this time around if I type in 500 in Subscriber Information it just asks me if I want to delete it (which doesn't work). There's probably something else I did that I just can't remember. The individual station voicemails work now that I've changed forwarding on busy/no answer to 529 but not the 500 mailbox. I'll have to see if I can find a laptop with a serial port but after reading the SVMI manual I don't see what setting I would have to change if I can get into the terminal.