You are being asked to upgrade because TurboTax Free Edition does not support form 1099-SA.  To report your 1099-SA information, you will need to upgrade to TurboTax Deluxe Edition or higher. 

Another option for filing your return (income restrictions apply) is to use the TurboTax Free File Program. The following TurboTax FAQ explains this program. https://ttlc.intuit.com/replies/3301359