Verify that the basis for prior years on Line 2 matches the amount on your 2018 (or latest) 8606 Line 14.

If it does not you can manually enter the correct amount by visiting the appropriate worksheet.

It does not match and seems to be a bug as it has been incorrect on my forms for years and years, I had a TurboTax rep call me and I showed them that it wasn't adding from year to year, they agreed that it was an issue beyond their knowledge.  They transferred me to the tax expert help line but I selected that I didn't want to pay the extra $90 for a personal consultation so the automated system disconnected me immediately. 

I guess I have to keep track myself as TurboTax can't keep track of a rolling total.

The 8606 is still in draft mode. It is not yet finalized.The 8606 is expected to be released February 5, 2020. Once released, Turbo Tax will be able to update and incorporate the final version. You can keep track here.

AmyC - it seems this hasn't worked for me since 2015 carrying forward the 2014 numbers, each year since seems not to reference the prior year.  Is it because I start entering information before the form is ready and then when it is ready the program doesn't update it since I've already gone through those screens?

Form 8606 is scheduled to be available on 2/12/2020.

You can check the most current form availability here:

IRS Forms Availability Table for TurboTax Individual (Personal) Tax Products

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State Forms Availability Table for TurboTax Individual (Personal) Tax Products