SBT Failing to download dependencies

I’m attempting to use a GitLab runner to build my Scala SBT project. Everything compiles fine locally, but when running in GitLab CI, sbt clean compile fails to download dependencies:

[error] sbt.librarymanagement.ResolveException: download failed

Is there a difference in how GitLab runners find and download SBT dependencies?
I’m using SBT version 1.1.1