Should I enter my 1095-a if I only had coverage for about half the year of 2018?the form says amount in row cannot all be zeros and wont let me proceed.

Yes, your 1095A form needs to be entered, even if you only had marketplace coverage for half the year.  For the fields with zeros, remove all of the zeros and leave the fields blank.  If you still have errors after doing this, DELETE the 1095A form and re-enter it leaving all the fields blank that have zeros on your 1095A form.