Failed to find target with hash string 'android-25'

Well, I was suffering with this Issue but finally I found the solution.

Problem Starts Here: ["Install missing platform(s) and sync project" (link) doesn't work & gradle sync failed]

Problem Source: Just check out the app -> src-build.gradle and you will find the parameters

1. compileSdkVersion 25

2. buildToolsVersion "25.0.1"

3. targetSdkVersion 25

Note: You might find these parameters with different values e.g compileSdkVersion 23 etc.

These above parameters in build.gradle creates error because their values are not compatible with your current SDK version.

The solution to This error is simple, just open a new project in your Android Studio, In that new project goto app -> src-build.gradle.

In build.gradle file of new project find these parameters:

In my case these are:

compileSdkVersion "26"    
buildToolsVersion "26.0.1"
targetSdkVersion 26

Now copy these parameters from your new project build.gradle file and post them in the same file of the other project(having Error).

You don't need to update anything. Just download the SDK for API 25 from Android SDK Manager or by launching Android standalone SDK manager. The error is for missing platform and not for missing tool.

Make sure your computer is connected to the internet, then click on the link that comes with the error message i.e "install missing platform(s) and sync project". Give it a few seconds especially if your computer has low specs, it will bring up a window called SDK Quickfix Installation and everything is straightforward from there.

I got similar problem

1: I tried to resolve with the answer which is marked correct above But I was not able to get the system setting which was quit amazing (On MacBook).

Most of the time such errors & issues comes because of replacing your grade file with other grade file ,due which gradel does not sync properly and while building the project issue comes . The issue is bascially related to non syncing for platform tools

Solution a: Go to File and then to Your project strucutre -modules -app-Properties -build tool version -click on options which is required for your project (if required build tool version not there chose any other). This will sync the grade file and now you can go to gradel and change target version and build tool version as per your requirement .you will prompted to download the required platform tool to sync it , now click on install tool version and let project to build

Solution b: Try Anuja Ans if you can get option of system setting and install platform tool.