I had same problem last year, it's taken me forever to figure out what to do, no thanks to turbo tax which was no help at all. You are right that you have to log into the mac as a different user. Then you need to transfer the tt file from one user to another. It worked for me, although I will never buy tt again for a mac, I use my Surface tablet now with no problems. Here's what I googled to tell me how to transfer files.
How to transfer files between two user accounts on your Mac
