Service issue

[Brian]

I referred a friend to VOIPo, who signed up, and got one of the adapters with the built-in routers. She's plugged it in between her cable modem and her internal network, but is having a lot of one-way audio issues. She's worked with support, but has not gotten any good resolution yet. I was just wondering if there are any common issues with this setup, or if it's likely a deeper problem. As it's directly plugged into the modem, I'm not sure what, if anything, is there to configure?

Just a side note, she said the adapter appears used, as it has "gunk" on it (her words).