I have just recently switched to using Photos instead of iPhoto but now I find I cannot share my pictures directly to Facebook. When I try to do that, it constantly says I need to fill in my Facebook password, which I've done, but it never accepts the password. I've even signed out and back in to my Facebook account and that password DOES work so why doesn't it work on Photos!
Have you enabled the Facebook account in the System Preferences > Internet accounts? Enable the "Share" button there.
If that does not work, try the fix in this document: If Share options or Markup is missing after upgrading to OS X Yosemite or El Capitan - Apple Support
The Share button is already checked. I tried Unchecking it, then re-checking it and it still didn't work. Without the Share button the option to share on Facebook doesn't even show up on the Photos menu. I'll try reading the article you listed. Thanks for trying.
Photos won't accept Facebook password
