@tacopeland and @cjcox. Great to hear it’s working for you.
Do you know if the AT&T Arris NVG589 is one of the routers that will not allow port forwarding involving port 443 or is it just the AT&T 2-Wire routers? I have tried it both with port 443 forwarding and without port 443 forwarding. Can still remotely access Tablo on Verizon wireless in both cases and cannot access Tabl from work wi-fi in both cases. Any reason not to forward port 443?
Just forward the two ports listed before, restart your router after the saved configuration, then restart your Tablo. Give it a try then.
But to be honest, it sounds like a work wifi problem if you can connect remotely over the Verizon network. Go to Starbucks!