watchguard xtm26 - moved

question if anyone has an ideas that might help:

moved a small network that has a slightly older watchguard xtm26 firewall. Was running on Time Warner cable with a static ip address, basically moved it where it's a similar Time Warner setup, just a different ip address.

Logging into it via internal ip address; it seems to have a somewhat crappy older interface that doesn't seem to match anything tech support suggests (which I'm pretty sure you have to log onto the watchguard website to use).

So, changed ip address in only place I see it as an option (I believe it was a screen for "interface".) Otherwise, I've gone through every screen and don't see anything else to change. The DNS addresses are a mix of TWC and Google, and are the same as before. But it isn't working... anybody have expertise with WG XTM26?

Part of me is beginning to think I have to either coordinate this change with the supplier who sold and serviced it for the first 3 years or with Watchguard direct (like maybe, it has to be sync'd with the mothership somewhere in the cloud before working). Any advice would be appreciated.