I'm not sure whether you saw the additions to my original reply.
For your SPA2102 with FPL, I recommend doing the following . . .
1. Navigate to the SIP tab-->NAT Support Parameters, and make sure that the following settings are enabled (due to FPL's switches):
a)Handle VIA received-->yes
b)Handle VIA rport-->yes
c)Substitute VIA Addr-->yes
2. Navigate to Voice-->SIP-->SIP Timer Values (sec)
Reg Retry Intvl should be 120 seconds
3. Navigate to Line 1 (or whatever you're using for FPL)-->SIP settings and change SIP Port to a random number between 30000 and 60000
Keep this link handy: freephoneline-ca-free-local-soft-phone- ... #p26808549 (it also applies to your ATA)
I also suggest reading the first four pages (the preamble) of this PDF guide, regardless of the ATA you own: http://forum.fongo.com/viewtopic.php?f= ... 805#p73839.
Also visit https://support.freephoneline.ca/hc/en- ... redentials and http://forum.fongo.com/viewtopic.php?f=15&t=16198