Are you referring to an e-filing pin?
No if you forget your 5 digit PIN it will not be reassigned. See What is the difference between the five-digit Self-Select PIN I created last year and my Self-Select...
If you have a copy of last year's return, the 5 digit self-selected efile Pin will be included in the Federal Information Worksheet, The worksheet is included in the PDF of the 2018 tax return that you can download if you used the online editions. If you filed a return with Turbo Tax in 2018, you can download and print the return, unless you filed using the free version on Turbo Tax.
The IRS has eliminated the use of a PIN to e-file your 2019 tax return. To verify your identity for e-filing will use last year's adjusted gross income (AGI) as your PIN.
You can get a copy of your 2018 tax return, from TurboTax it will have your AGI. Follow these steps to get a copy of your prior-year tax return.
Sign in to TurboTax making sure you're using the same TurboTax account (with the same username) as in prior years.
This link How do I access a prior year return? has additional information that you may find useful.
However, if you need an IP PIN to file your taxes and you lost your CP01A letter (or never received it), you can: