Failed to find Build Tools revision 27.1.1. When I try to download, says it has no download link:

Referring the official documentation, the actual release is:

android {
    buildToolsVersion "27.0.3"
    ...
}

and not 27.1.1

so, fix your android node with

android {
  compileSdkVersion 27
  buildToolsVersion '27.0.3'
   .....

According to the Android SDK manager, the latest version of build tools are 27.0.3 and 28.0.0-rc1.

27.1.1 is the support libraries version.

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