I tried this morning (8:35a CT) and could not. I then called and was told I had to buy it. After insisting he was wrong, politely, I got an economy plus seat. When I checked-in, I was able to choose any e+ seat.

But, it did not upgrade me to first. Instead the site tried to sell me an upgrade. I thought it was all being activated today?

So, I called again, CS referred me to web support who told me I still had to make the request at the airport. So, I asked for the Elite desk number and called there. After about 10 more minutes with them, they said the same thing - ask at the airport.

So, it looks like they'll still be selling them to non-elites before offering them to CO elites until mid-October (at least that's what the UA elite desk told me).