Run SERVER_PREP.bat to prep the modpack to run as a server.
Alternatively, you can manually delete the files below, if they exist.

===FILES TO DELETE===
config\mod-director\better_horse_hud.url.json
config\mod-director\better_invalid_session.url.json
config\mod-director\chatflow.url.json
config\mod-director\craftpresence.url.json
config\mod-director\custom_loading_screen.url.json
config\mod-director\default_world_generator.url.json
config\mod-director\dynamic_surroundings.url.json
config\mod-director\flying_cullers.url.json
config\mod-director\its_the_little_things.url.json
config\mod-director\modernity.url
config\mod-director\music_for_hardcore_ender_expansion.url.json
config\mod-director\notenoughkeys.url.json
config\mod-director\optifine_D6.url.json
config\mod-director\optifine_E7.url.json
config\mod-director\options_enforcer.url.json
config\mod-director\pixel_reality_atmosphere.url.json
config\mod-director\pixel_reality_luminance.url.json
config\mod-director\render_player_api_enhancer.url.json
config\mod-director\skinport.url.json
config\mod-director\smart_render.url.json
config\mod-director\smooth_font.url.json
config\mod-director\sound_filters.url.json
config\mod-director\triangulator.url.json
mods\BetterFoliage-MC1.7.10-2.0.17.jar
mods\BetterHorseHud-1.7.10-1.0
mods\BetterInvalidSession-1.7.10-1.0.3.jar
mods\BetterLoadingScreen_GO.jar
mods\ChatFlow-1.1.jar
mods\CraftPresence-Forge-1.7.10-Release-1.8.8.jar
mods\DefaultWorldGenerator-1.7.10-0.1-b13-universal.jar
mods\DynamicSurroundings-1.7.10-1.0.6.4.jar
mods\FlyingCullers-1.7.10-1.3.jar
mods\itlt-1.7.x-1.0.3.jar
mods\Key-Bindings-Overhaul-Mod-1.7.10.jar
mods\LumySkinPatch-1.0.10.jar
mods\NotEnoughKeys-1.7.10-3.0.0b45-dev-universal.jar
mods\OptiFine_1.7.10_HD_U_D6.jar
mods\OptiFine_1.7.10_HD_U_E7.jar
mods\OptionsEnforcer-1.7.10-1.3.jar
mods\RenderPlayerAPI-1.7.10-1.4.jar
mods\RenderPlayerAPIEnhancer-1.7.10-1.4.jar
mods\SkinPort-1.7.10-v10d.jar
mods\SmartRender-1.7.10-2.1.jar
mods\SmoothFont-1.7.10-1.15.3.jar
mods\SoundFilters-0.8_for_1.7.X.jar
resourcepacks\GO_resources.zip
resourcepacks\HEE_Music_v1.0.zip
resourcepacks\Modernity-format1-v*.zip
resourcepacks\Pixel_Reality_Atmosphere.zip
resourcepacks\PR_Luminance_V1.1.zip