I didn't receive my 5 digit signature number

[vnanta]

I didn't file with TurboTax last year

[ReginaM]

You no longer need a PIN number from last year to electronically file your return as the IRS did away with this method of security validation.  Instead you will be required to use your 2018 AGI (Adjusted Gross Income) in order to electronically file your federal tax return.

You can obtain a copy of last year's tax transcript online using IRS link:   Transcript 

OR

If you have a copy of your 2018 tax return, your AGI is located on line 7.