Trentalia

If you are starting at Malpensa airport, Trenitalia probably cannot sell Malpensa Express tickets. You can probably buy Milano Centrale to Bologna tickets if you are inside the 120 day period.
Malpensa Express is a regional train with advance purchase restrictions. And it is operated by Trenord, not Trenitalia. You can just buy that ticket after you land at Malpensa.

From Milan Airport to Bologna what is the meaning of the shopping cart with the red line thru it? Just that you can't buy the ticket online?

If you hover the mouse over the barred cart you'll get the answer you need (in rotten English, imho).
In short, there is a 7-day limit for online purchase of regional trains tickets. Not a big deal as you can't reserve a seat on regional trains and there are no discounted fares. Buses on rails: first come, first served.
Malpensa Express is jointly managed by TreNord and Trenitalia, so you can get tickets here, too, and avoid this problem.

It is not recommended, in fact, highly discouraged from buying Regionale train tickets on line because on-line tickets come pre-validated AND with a four hour window from the time your specify on the ticket. Regionale train tickets should be purchased at the station and then validated (time stamped) just prior to boarding the train. Just watch the locals do it - validation that is !