When you don't have any tabs (groups) in your contenttypes, the translate tab with the languages is not shown. Adding a group fixes the problem.
This is probably not an issue that is very common, because when you use the readme as described, you automatically make a group called content.
I just stumbled upon it because I have reorganised the whole contenttypes.yml in my project, and deconstructed the whole thing. :)
Details
- Translate Version: 4.1.5