Don't want to give up but...
None of my vocabulary decays. My word strength is always strong.
I want to practice the words I made mistakes on or haven't seen in a while. WIth no decay, this is not possible and I end up mostly practicing the words that I already know.
Is there any solution? Have I overlooked some option?
Duolingo can be buggy, at times. If you're truly not experiencing decay, then send feedback to Duolingo. Duolingo's staff are typically very responsive to user's concerns.
It looks like you have only been doing Duolingo for a week. Give your tree some time, it will decay. Geez, I wish my tree was so young and didn't have lots of decayed leaves.
If you keep progressing through the tree, you will end up reviewing prior material as you learn more material. So, until, you have to go back and review, progress and learn more Spanish. You will review the words and concepts that you didn't understand perfectly just by doing the new lessons.
Believe me, those leaves will decay soon enough.
I have been more than two weeks and my word strength also does not decay -- if I go back and practice prior sessions then sometimes some words are highlighted in blue and if I hover over them it tells me when I last saw them but it's got nothing to do with whether I know them or not.