Hi Barbara, I hope you are well. If you want to continue troubleshoot book ordering this week just let me know. I will recap on some questions I wanted to ask. I will copy/paste them from earlier.
Do you see any error message text? Does it say 'Unknown Error' and any error numbers?
Can you type the exact error message if there is one?
What kind of Internet connection are you using? Is it broadband? Is it usually good quality/speed?
Do you know of any firewall, or anti-virus software, or system cleanup apps like MacKeeper that you are using on your Mac?
99 times out of 100 this is a network issue. If you could possibly try a different Internet connection, this would be the easiest most effective test. For example if it is a wireless connection try to get a better strength signal, or connect from the computer to the router with a network cable.
Let me know if you have any questions on any of this, best regards!