If I used a pin last year and not the agi, how can I try to refile using that pin?

You can't use that PIN again.  According to the IRS:

 

• An IP PIN is valid for one calendar year.
• A new IP PIN is generated each year for your account.
• Logging back into the Get an IP PIN tool, will display your current IP PIN.
• An IP PIN must be used when filing any federal tax returns during the year including prior year returns.
• FAQs about the Identity Protection Personal Identification Number (IP PIN)

How to get an IP PIN

The fastest way to receive an IP PIN is by using the online Get an IP PIN tool. If you wish to get an IP PIN and you don’t already have an account on IRS.gov, you must register to validate your identity. The IP PIN tool is generally available starting in mid-January through mid-November. Select the following link to get started:  Get an IP PIN

 

 

The PIN used at the time of filing is for that you only.  You have to set a new one each year.  You must use last year's AGI.  However, if you used TurboTax and sign it, it remembers your AGI from last year.