Gradle crushes with GeckoLib in MCreator

When I installed GeckoLib in MCreator and when I turned this plugin on, the Gradle said that that "MCreator detected Gradle failed to properly complete the build" and the console showed me this: 

FAILURE: Build failed with an exception.
* What went wrong:
Could not resolve all files for configuration ':compileClasspath'.
> Could not find software.bernie.geckolib:forge-1.15.2-geckolib:2.0.0_mapped_snapshot_20200514-1.15.1.

...

I don't know what to do with this. Without Gradle, my project won't appear in Minecraft. Please help.