Can’t complete lessons, button missing

I realy like LearnPress LMS. It’s almost perfect – but I have a huge problem.

I almost finished my first course, and I would like to launch it but I’m not able to make done any lesson because the comlete button is completly missing.
I’m enrolled to the course, I can read, I can leave a reply, but I can’t take the test – the lessons must be done before.
I tried to turn off all the plugins – it didn’t solve the problem. I tried to change the template – same result. I haven’t any idea what’s the matter. If I can’t fix it, I have to find other lms. 🙁