Modpack version
1.35

Issue
I can't remake your server version of Enigmatica2: Expert Sky Block, for added some plugins on server. And I can't added sponge core on your server. How I can install plugins on your server core.
Please help.

My modpack is for Forge, and Forge does not support plugins. You're on your own with SpongeForge.
The modpack already contains server utilities, via the mod FTB Utilities.