A 2016 tax return can only be printed and mailed, it cannot be e-filed.  Is this where the program is hanging?

No. I am doing mailing. This is at File a return-->File your Federal Return -->File by Mail-->Select the returns you're ready to file by mail -->How do you want your federal refund -> Select Direct deposit or Mail me a check

Are you using the Online version?  Online is only for 2017 now.  So you have to use the Desktop program to do a prior  year.
<a rel="nofollow" target="_blank" href="https://turbotax.intuit.com/personal-taxes/past-years-products/">https://turbotax.intuit.com/persona...>

If you filled out your 2016 info in the 2017 online version you have a problem and you should not file it.

I am using the desktop version as I can file 2016 only using the desktop version

Anyone with an OS X 10.13 system has major issues with the  2016 filing process, .even for selecting the file-by-mail.
.....since the OS X 10.13 system came out long after the software was written...(at least in the developers opinion...or manager's decisions)
..
TTX claims they won't fix it...but provides this somewhat flakey workaround...where you have to use Forms Mode" and select the forms you want to print one-by-one:

https://ttlc.intuit.com/questions/4139594-turbotax-mac-turbotax-2016-becomes-unresponsive-after-upgr...