Do I type a "0" or fill in the loss box and put the numeral down - VA form 760 line 15. The instructions do not say. My result is negative.

It sounds like you are trying to filing a Virginia return using the married filing separately status but you don't have any income from Virginia.  If this is the situation, then you would only be required to file a tax return in Virginia if your Virginia adjusted gross income is more than $11,950.  You would not need to worry about an audit if you don't have any Virginia source income. Please see the excerpt below from the instructions for Form 760.

If you still want to file a Virginia return and prepared your married filing joint return using TurboTax, please see this link for guidance to help you prepare the state returns. You can enter zero on Line 15 and will need to mail the state return in.  You will not be able to electronically file your married filing separately state returns.