Today I was trying to make a fresh start and I had this error.
C:\forge>gradlew setupDevWorkspace --info
Starting Build
Settings evaluated using empty settings script.
Projects loaded. Root project using build file 'C:\forge\build.gradle'.
Included projects: [root project 'forge']
Evaluating root project 'forge' using build file 'C:\forge\build.gradle'.
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/mojang/authlib/1.5.16/authlib-1.5.16.pom]
Resource missing. [HTTP HEAD: http://repo1.maven.org/maven2/com/mojang/authlib/1.5.16/authlib-1.5.16.jar]
Resource missing. [HTTP GET: http://files.minecraftforge.net/maven/com/mojang/authlib/1.5.16/authlib-1.5.16.pom]
Resource missing. [HTTP HEAD: http://files.minecraftforge.net/maven/com/mojang/authlib/1.5.16/authlib-1.5.16.jar]
Resource missing. [HTTP GET: https://oss.sonatype.org/content/repositories/snapshots/com/mojang/authlib/1.5.16/authlib-1.5.16.pom]
Resource missing. [HTTP HEAD: https://oss.sonatype.org/content/repositories/snapshots/com/mojang/authlib/1.5.16/authlib-1.5.16.jar]
FAILURE: Build failed with an exception.
* What went wrong:
A problem occurred configuring root project 'forge'.
> Could not resolve all dependencies for configuration ':classpath'.
> Could not find com.mojang:authlib:1.5.16.
Required by:
:forge:unspecified > net.minecraftforge.gradle:ForgeGradle:1.2-SNAPSHOT
* Try:
Run with --stacktrace option to get the stack trace. Run with --debug option to get more log output.
BUILD FAILED
Total time: 6.586 secs
I had the same also with gradlew build.