Ok, so this topic has been identified and never resolved by Google. (Like most issues with their entire wifi line.). But I may have found a solution! Unfortunately Google closes topics so quickly that you can't reply to the large threads where people complain about the same issue. So, here goes...
When trying to set up or change your static IP address through the app, after hitting the save icon, the yellow wheel just spins forever and never updates the router. You can factory reset the network, set up all your mesh points, and every time you won't be able to put in your static IP. This issue has been reported again and again with no resolution.
After resetting my network several times, I think I found a combination of steps that works.
1) Reset your network from the app....twice. the first time resets all the points, the second time removes it from your profile. (Such a weird workflow Google.)
2) Set up your network from scratch. (You can use your previous SSID and password.) Set up every additional mesh points in the initial setup. (In my case I use three additional points and an additional router with backhaul wiring to reach the maximum recommended 5 points.)
3) after all your points are set up and you successfully pass the mesh test, unplug every point from power. Including the router.
4) turn off cellular and wifi on your phone.
5) plug in ONLY your modem Ethernet connection to your router
6) plug in the power to your router
7) turn the wifi on for your phone and connect to your WiFi network
😎 you should be able to go to the home app and open the wifi section. Go to the advanced settings.
9) unplug the router Ethernet cable
10) go into the WAN settings and select static
11) input your static IP info
12) after hitting done, select the floppy disk save icon at the top right to commit your changes.
13) This should finally update your static IP settings! Then you can go power back on all your additional points and complete network and mesh tests.
I hope this helps someone, because I've been fighting with this god awful system to the point I was ready to follow the crowd and ditch it for an Netgear orbi setup.
