Hey,
Eclipse tells me that the is no source attachment for forge-1.14.4-28.1.90_mapped_snapshot_20191123-1.14.3.jar .
So I ran "gradlew eclipse" again and looked at the process. I found an interesting line, but I don't know how to fix this error.
Error getting artifact: net.minecraftforge:forge:1.14.4-28.1.90_mapped_snapshot_20191123-1.14.3:sources@jar from MinecraftUserRepo