Also, what is the WAN IP on your Time Capsule? If it’s an internal IP you could be engaging in Double NAT which would cause issues. Internal IPs start with 192., 10., or 172.
If that’s the case, your modem is not in bridge mode, which is causing your problems due to Double NAT. See the links below for an explanation.
http://www.practicallynetworked.com/networking/fixing_double_nat.htm
So if your modem is running a built-in router and you have a Double NAT situation, please see this thread on the forums:
https://community.tablotv.com/t/router-needs-manual-configuration-error-ports-open-on-router