Error when setting up modding environment "Could not resolve all files for configuration ':runtimeClasspathCopy'."

The error:

Could not resolve all files for configuration ':runtimeClasspathCopy'.
> Could not find net.minecraftforge:forge:1.17.1-37.0.103_mapped_official_1.17.1.
  Searched in the following locations:
    - file:/C:/Users/Back to the future/.gradle/caches/forge_gradle/bundeled_repo/net/minecraftforge/forge/1.17.1-37.0.103_mapped_official_1.17.1/forge-1.17.1-37.0.103_mapped_official_1.17.1.pom
    - file:/C:/Users/Back to the future/.gradle/caches/forge_gradle/bundeled_repo/net/minecraftforge/forge/1.17.1-37.0.103_mapped_official_1.17.1/forge-1.17.1-37.0.103_mapped_official_1.17.1.jar
  Required by:
      project :

Possible solution:
 - Declare repository providing the artifact, see the documentation at https://docs.gradle.org/current/userguide/declaring_repositories.html

Apparently it's struggling to the file. I did check in the corresponding folder and the files were there. What should I do?

There's also another separate error report in the same build process. Don't know if it matters or if the two errors are connected. 

Caused by: java.util.zip.ZipException: zip END header not found

I'm still new to this modding thing so any help is appreciated! :)