I don't have an HSA but it is telling me that line 12a is my HSA, this is the first year this has happened. Any advice on how to proceed?

Health Savings Account (HSA) contributions that were made either by you or by your employer on your behalf are reported on your W-2 in box 12 with code W.  If your W-2 is showing something in box 12 with code W, but you do not have an HSA, then you should contact your employer for clarification.  If this information was reported on your W-2 in error, then they should issue a corrected W-2 removing that information.  

If you learn that the information is correct, and you do have an HSA, then TurboTax will guide you through the process of entering information about your HSA account when you go to the Deductions and Credits > Medical > 1099-SA, HSA, MSA section of your return.