Why I can't to go further in sololeearn.

Question

I have completed the 64 stages of java programming language.

Answer 1

Is 64 got √ tick? Can't open 65 lesson ?
Close and reopen app.. Then see.
Try update version if not worked. If thr problem still exist, then mailto: [e-mail] with details..

Answer 2

Make sure you've completed all the rest of lesson 64. You can check this by going to the "main tree" of whichever language you're learning and then starting at the beginning and scrolling through each screen until you can't, except if you hit the continue button down the bottom or answer one of the unit questions.
If that doesn't work, do as Jayakrishna said