I have TT Premier. When I select TT, setup new return, it asks me to login to my Intuit Acct. When I login the TT program shuts down. I have a IMac.

[Critter]

Why are you logging in online when you have the downloaded program ?  If you installed the program on your computer you open the program to complete a return ... you do not log in online. 

[cctfuller]

Thanks Critter#2.  I can't get past the Intuit Account login screen to setup a new return.

[Critter]

It may be best for you to talk in real time to TT Customer Support . They can even screen share with you if necessary to see what is going on.  
Here's how to be assigned a phone number to the proper department at TT Customer Support during the business hours shown below (it will not display when they are closed).

1) Go to https://support.turbotax.intuit.com/contact/
2) Choose the product platform you are using.
3)  Ask a question or keywords without quotes, and Submit.
4)  On next page, skip the suggested articles if they don't help.
5) Scroll down, and you should be able to enter the Support module to get a phone number. (That will be grayed out when they are closed).