failed to find target with hash string android-23
In my case, clearing caché didn't work.
On SDK Manager, be sure to check the box on "show package descriptions"; then you should also select the "Google APIs" for the version you are willing to install.
Install it and then you should be ok
In Android Studio File -> Invalidate Caches/Restart solved the issue for me.
The answer to this question.
Gradle gets stupid from time to time and wiping out the cache is the only solution that I've found. You'll find a hidden .gradle folder under your user home folder and another one wherever the checkout location is for osmdroid.