Ok after 2 days I got my Sanctuary Settlement to 100. First the size was green (not yellow) so I figured that was the reason it wasn't giving me the trophy, so I built some wooden crates and it turned yellow, still at 100, nothing. I then maxed out size where bar is full and couldn't build anymore, that didn't work either.

I then reloaded an old save at 99 happiness made size yellow FIRST with crates then reached 100, nothing.

BTW my internet was unplugged for all this because I have the 1.03 patch and that 30 sec save bug happens if my net is plugged in. So anyway next I plugged it (the internet) back in and dealt with the 30sec bug and still wouldn't give me the trophy! I don't know what to do anymore or wtf is going on.

UPDATE: It finally gave it to me but never popped up on screen. Looking at the time it gave it to me the very first time I should of gotten it (i think even before having a large settlement I've read that works for some people [getting it without having large settlement yellow not green]. It check the screenshot while sharing the achievement (to see the screenshot) and it was took while I was waiting on a bench. So if you get an achievement while in the middle of sleeping or waiting it doesn't pop up on screen I guess?

BTW I deleted my game data as to get rid of the 1.03 patch to see if that was the problem and reverted to 1.00, I let it go to 100 again from a save and it didnt pop up i then checked my trophies and it was there but the time it had was from way earlier.

So basically, I'm guessing I got the achievement while waiting, it didn't pop up and since I already gave it to me thats why it had no reason to pop up later when i kept going from 99 to 100. Even though I already checked for it 3 times in the trophies section after synching, just took awhile to show up there for some reason. Oh well whatever at least I finally got it.