Android failing to build when signed

Hello,

I have tried to create a keystore for my app. Whenever I create one, my project wont build. Using the debug (unsigned) keystore works, but using my own keystore causes it to fail.

Upon hitting 'Build and Run', I get the error;

 Unable to install APK!
 Installation failed. See the Console for details.

After checking the Editor Log, the last two lines are;

 Native extension for OSXStandalone target not found
 Native extension for Android target not found

If I use the unsigned debug keystore this doesn't occur. When I use my custom keystore I can't build. I don't understand why this is happening.

Thanks in advance.