can't share complete tree achievment on facebook

[TomZZZ]

a little window opes and immediately closes... any idea why?

[Sam_uk]

Same problem here. I want to boast! Fix it! LOL

[yimantuwingyai]

I'm experiencing this as well. Every time I level up I want to share it on Facebook and then it disappears. I want to promote this site other than just saying "Duolingo is cool". Also I want to brag.