The IRS is no longer issuing 5 digit PIN's for use as an electronic signature for e-filed tax returns. You have to use the prior tax year AGI, ie the 2015 AGI for the tax year 2016 federal tax return. Or you can use the 5 digit self-selected PIN from the prior tax year.
See this IRS website for information - https://www.irs.gov/individuals/electronic-filing-pin-request
