Build failure while setting up local workspace

i followed the steps mentioned in Set up a local workspace - JabRef Development Documentation

when i do ./gradlew assemble

got this error

FAILURE: Build failed with an exception.

Could not resolve all files for configuration ‘:runtimeClasspath’.
Could not download javafx-controls-15.0.1-linux.jar (org.openjfx:javafx-controls:15.0.1)

sounds like it’s a temporary issue