Pin numbers used on 2016 taxes was rejected on 2017 and 2018 taxes. What is going on? I can't get through to turbotax to ask them.

[macuser_22]

What pin?  The 5 digit self selected pin or the 6 digit IP PIN?

  The IRS must issue a new IP PIN each year.  If the 5 digit self selected pin does not work then use last years AGI instead.

[BMcCalpin]

If you are missing the IP pin (Identity Protection), then macuser_22 is right that this pin is re-issued every year (usually sent to you in December by mail, as I recall).

If you did not receive the letter or have lost the letter, then please see https://www.irs.gov/identity-theft-fraud-scams/get-an-identity-protection-pin for how to get a replacement.