Build properties not found for package Android SDK Platform 25

I've deleted the version 26 from my sdk platforms folder ( C:\Users\[MY USERNAME]\AppData\Local\Android\Sdk\platforms , i.e. android-26 ) . I've then closed android studio and when opening it , i've right-clicked it and opened it with 'Run as Administrator' .

this fixed the issue on my end.

Go to Tools -> SDK Manager on Android Studio. Tick the missing SDK and click apply. It will download and install the required SDK. That solved my issue.