crashing when i run a test environment when using geckolib as a mod

Whenever I try to run a test environment, it crashes. I am using geckolib and klsts metroid mod for the mods on the run folder. Besides that, i did nothing with the files. I tried to use the geckolib plugin, but it still crashes. When I run it without geckolib, it doesn't crash, it says klsts metroid requires geckolib, and I can't use geckolib, so that will be impossible to play with that mod, and it needs klsts metroid because its made to work with it.