Try again through the day. Keep trying tomorrow. Sometimes Google servers get "funny". In the medical field they call it an ideopathic condition - and it means the same as it does here. "We're standing in a field of clues, up to our necks in them, and can't find one." They eventually get things running.
BTW, you might try rooting, then running Safestrap. It makes things like this a lot easier. You can totally unroot one ROM and totally rip another one up. And if you flash a completely unworking ROM it takes about 1 minute to get the phone running again (to do a restart). You can even install a stock unrooted ROM to the stock slot, then install rooted ROMs to other slots - and boot to whichever one you want at the moment. When you're going to do something that has the slightest chance of going wrong, do a backup of that ROM. Then if things go wrong, just restore it. (I flashed a keyboard as a ROM once. Deleted that slot and booted into one of the working slots. What could have been "oh, s**t, what do I do now" was just "there goes another 2 minutes I'll never get back".) I won't upgrade to 4.4.4 if AT&T pushes it (and forget about Lollipop) unless someone updates Safestrap to run on them. It's like updating from a Chevy to a Mercedes - but it comes without brakes.