I just figured it out - for anyone else having this issue: Right-click on the file and "Get Info", then turn down the arrow by the "Name & Extension" details an...

@stuartcrawford did you figure out how to import your TXF files on Mac? I am having the same issue - the files are grayed out even after changing the extension ...

Right-click on the file and "Get Info", then turn down the arrow by the "Name & Extension" details and you'll see that the extension didn't change like you thou...