Turbotax 2019 and it says I need Mac OS X 10.12 or above. I have OS X 10.12 but when I try to open it it says I need OS X 10.13. Is anyone having this issue?

The version of Mac OS you will use will be determined by the browser version you are using. The online return requirements can be found here. 

If you need additional assistance, please contact customer support.