I cant share to my fb feed

This has been happening for months now but never looked into it because I can just copy and paste but thats a pain . So if I see a interesting article i hit the share and then (to fb) and the fb icon will flash almost like a screenshot type flash and then I will go to fb and it never will share ???? Whats the deal ? And if I share to my neighbor app or text or email it works fine .. thanks in advance