What did I do wrong. Changing the Default IP failed

Hi all - A few weeks back, I posed a question on here as to whether or not changing my default IP would be an easy or catastrophic process.

After the general consensus, it seemed, was that changing the IP was doable, and that doing so would simply force the other UniFi devices to fall into line and use the new IP I gave it, I tried it out.

My Gateway - a CGU - moved over fine, but all other UniFi devices - switches an APs - failed at adopting, and it seemed like I would need to reset everything and start all over (my worst nightmare - I.e., what I was hoping I didn’t need to do).

When I moved the CGU back to its initial IP, everything came back.

So, where did I mess up? I feel like there‘s a chance I may not be not providing enough detail for you all to do the postmortem, so to speak, so let me know what other info, if any, is needed. Thanks everyone.