Skill strength bar doesn't increase
The problem exist mainly in mobile, but sometimes in web too. When i complete a practice course to the skills, which are not fully strength, after the completition the system just doesn't increase the strenght bar, the program represent the 'congratulations, your strength are good now, keep it strong', and i receive the XP points for the course, but nothing happens with the strength bar. It's quite demotivating : (. I feel some increasement of this failure in the application, since the last update, but this annoying problem is exist continually.
I'm going through this as well. I did one strengthening activity five times, and STILL it's not gold yet. If I look at the bar, it's got the tiniest sliver of grey.
Sometimes I have to do two practice lessons to turn a skill gold again. This is particularly true when the skill set has a lot of lessons in it. I think that one review just does not have enough questions in it to cover all the words in a skill set with 8-10 lessons. Try doing another review and see if your strength bar goes all the way up.
Recently, this started happening to me also. It is frustrating to me. I took a month off of DUO for the summer and now I have a lot of skills to strengthen. I am receiving 10 points for doing the strenghtening but not going gold. I must be OCD because I like to keep a gold tree :) I initially thought it was because I had missed a few of the strengthening questions. But I can ace the strengthening exercise and still not receive five bars (gold). It is acting like a bug because it never acts the same way each time. At times, I receive the gold and other times, the strengthening exercise never advances to the end page that shows you your strengthening level. FYI, I use Mozilla Firefox. I will download Google Chrome and try again.