Practice doesn't increase strength
I think I've been doing it (in French) for about two weeks, almost every day, and it hasn't increased a single skill in that time. Is it normal?
The same thing happens in Italian. Several times I have done a strengthening exercise as many as three times successfully but the strength bar showed no increase and once it decreased. This has happened to me so far only when using the mobile app. Update: I just spent two hours strengthening Future Perfect verbs and when I finally succeeded... NO INCREASE! Thanks for the boost to my ego DL!
It depends on your strengthen method.
give my favourite method a try for a few weeks
sometimes it is impossible to make a skill gold by strengthening. That is a well-known bug.
Repeat the lessons in that skill, starting at the last one
I also faced the similar problem in Spanish on iOS version 7.1.1. The strengthening bar sometimes does not increase even I pass the strengthen exercise (although not with full hearts).
Yes, I have one particular lesson in Spanish that seems stuck at 4/5 no matter how many times I strengthen skills on it.
The progress in the tree on android does not get updated often. That results in different trees in the browser and in the android app:
For me it has nothing to do with the platforms. I have tried doing a strengthening exercise both on the App and on a PC on the browser and while I completed with three stars because there really isn't anything else unfamiliar in the exercise, I am still stuck at 4/5...both on PC and App.
Actually this has nothing to do with platform or language as far as I know. It's just random lessons that are getting messed up. Duo's already said that they've been working on tihs a few months ago (lost the thread with comment) so I have no idea why it hasn't been fixed. I've basically given up on practicing old lessons and just doing new ones now.
I'm noticing the same thing in Spanish. Since the addition of the scorecards, I haven't been able to bring any of my subjects back up to gold through practice. I've been seeing my gold tree losing some luster, despite practicing working to maintain that in the past. Is there some other problem going on here?