Can I assume that, when you say you are connecting to your router,you are NOT using the router part of the ATA? You should have nothing connected to the WAN connection.
I have set one up for a friend and it does register with Voxalot - sadly though it keeps losing registration - why, I don't know, because my SPA-3000, with similar settings, works absolutley fine.
Another thing to note is that there are, effectively, 2 IP addresses to consider - you have probably worked this out anyway but I am mentioning it just in case.
There is an IP for the router then there is a separate IP for the ATA part. The router, as far as I can see, is useless in the UK and Australia because it uses PPoE and, in the civilised world (tic)
, we use PPoA.