All is in the title, this is the console output :

 

A:\Titouan\Développement\NewdyMod                                                                                                                    
λ gradlew genEclipseRuns                                                                                                                             
Starting a Gradle Daemon, 1 incompatible Daemon could not be reused, use --status for details                                                       
                                                                                                                                                     
> Configure project :                                                                                                                                
Java: 12.0.1 JVM: 12.0.1+12(Oracle Corporation) Arch: amd64                                                                                          
New Dep: net.minecraftforge:forge:1.16.2-33.0.23_mapped_snapshot_20200514-1.16                                                                       
Copying local object: c0/c05cbd8c88b5878703898150e157af88a29d8091 Asset: realms/textures/gui/images/6.png                                            
realms/textures/gui/images/6.png Hash failed.                                                                                                        
                                                                                                                                                     
> Task :downloadAssets FAILED                                                                                                                        
                                                                                                                                                     
FAILURE: Build failed with an exception.                                                                                                             
                                                                                                                                                     
* What went wrong:                                                                                                                                   
Execution failed for task ':downloadAssets'.                                                                                                         
> Failed to get asset: realms/textures/gui/images/6.png                                                                                              
  Some assets failed to download or validate, try running the task again.                                                                            
                                                                                                                                                     
* Try:                                                                                                                                               
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights. 
                                                                                                                                                     
* Get more help at https://help.gradle.org                                                                                                           
                                                                                                                                                     
Deprecated Gradle features were used in this build, making it incompatible with Gradle 5.0.                                                          
Use '--warning-mode all' to show the individual deprecation warnings.                                                                                
See https://docs.gradle.org/4.10.3/userguide/command_line_interface.html#sec:command_line_warnings                                                   
                                                                                                                                                     
BUILD FAILED in 46s                                                                                                                                  
6 actionable tasks: 6 executed                                                                                                                       

Thanks for responses

I've already restarted it many times, always the same error.

Where is the Gradle Cache directory ?

I've just tested remove just this file AND all the forgeGradle cache and the same error on the same file

No I deleted juste the .gradle/caches/forgeGradle directory