If you don't remember your 5 digit PIN, you do have another option moving forward.
The Self-Select PIN is a random 5-digit number that you enter as your electronic signature when e-filing your return. You can reuse your Self-Select PIN from last year or enter your AGI from last year's tax return.
For identification purposes, you need to enter either last year’s Self-Select PIN or your AGI. The IRS requires your AGI for identity verification. Please read the TurboTax Help Article listed below, to learn how to locate your AGI.
How to Locate Your AGI