Lesson Strengthening Issues
For some reason I am having issues with my lessons not strengthening.
Sometimes when I successfully finish strengthening a lesson I am not awarded anything.
Other times when I finish, I am awarded the ten points for the lesson but the strength meter does not change.
This is very discouraging especially after I try to strengthen the lesson more than once and nothing happens.
You should always get XP. Sometimes there are enough words weak that one strengthening won't move you to the next strength bar. Sometimes there's just a word or two that hasn't come up in your strengthening that's keeping you from moving up. This is more or less a bug, and the standard fix is to redo the constituent lessons of the skill.
For whatever reason, there are sentences in the lessons that just seem to never ever come up in strengthening, and if those happen to have weak words in them (which is likely, since you probably haven't strengthened them), then they're the culprits. Yes, Duolingo really ought to fix this, but instead it might even be getting worse: https://www.duolingo.com/comment/22496670
I've had that problem a lot. Sometimes I get around it by doing the strengthen using the timer function.