Hast du einen anderen server über den port 25565 laufen? Weil der server den du starten willst nicht auf dem selben port starten kann, weil ein anderer auf 25565 läuft.
Gehe in die server.properties, und suche nach dem port, da gibst du dann eine 5 stellige zahl ein z.b 25566 oder 12345.
Wichtig ist: der port den du für den anderen server willst muss sich von 25565 unterscheiden.
Wie MrMeepHD sagte, es liegt nicht an bungeecord, aber hast du vlt ein Plugin, was dies tut?
Mit was hast du es versucht?
Mit dem Launcher
Oder auf Minecraft.net?
Ps: Was für ne leitung hast du?
Vielleicht liegt es an deinem Intetnet
Oder an deinem Internet explorer?
Vlt versuchst du es ja mit einem anderen explorer.
Warning, your max perm gen size is not set or less than 128mb. It is recommended you restart Java with the following argument: -XX:MaxPermSize=128M
Please see http://www.spigotmc.org/wiki/changing-permgen-size/ for more details and more in-depth instructions.
Loading libraries, please wait...
[15:54:31 INFO]: Starting minecraft server version 1.8.8
[15:54:31 INFO]: Loading properties
[15:54:32 INFO]: Default game type: SURVIVAL
[15:54:32 INFO]: This server is running CraftBukkit version git-Spigot-db6de12-18fbb24 (MC: 1.8.8) (Implementing API version 1.8.8-R0.1-SNAPSHOT)
[15:54:32 INFO]: Server Ping Player Sample Count: 12
[15:54:32 INFO]: Using 4 threads for Netty based IO
[15:54:32 INFO]: Debug logging is disabled
[15:54:32 INFO]: Generating keypair
[15:54:33 INFO]: Starting Minecraft server on *:25565
[15:54:33 INFO]: Using epoll channel type
[15:54:35 INFO]: Set PluginClassLoader as parallel capable
[15:54:35 ERROR]: Could not load 'plugins/AdminTools.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: net/goobsygames/admintools/main/Main : Unsupported major.minor version 52.0
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:135) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:329) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
at org.bukkit.craftbukkit.v1_8_R3.CraftServer.loadPlugins(CraftServer.java:292) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.DedicatedServer.init(DedicatedServer.java:198) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:525) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
at java.lang.Thread.run(Thread.java:745) [?:1.7.0_121]
Caused by: java.lang.UnsupportedClassVersionError: net/goobsygames/admintools/main/Main : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.7.0_121]
at java.lang.ClassLoader.defineClass(ClassLoader.java:803) ~[?:1.7.0_121]
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.7.0_121]
at java.net.URLClassLoader.defineClass(URLClassLoader.java:442) ~[?:1.7.0_121]
at java.net.URLClassLoader.access$100(URLClassLoader.java:64) ~[?:1.7.0_121]
at java.net.URLClassLoader$1.run(URLClassLoader.java:354) ~[?:1.7.0_121] at java.net.URLClassLoader$1.run(URLClassLoader.java:348) ~[?:1.7.0_121] at java.security.AccessController.doPrivileged(Native Method) ~[?:1.7.0_121]
at java.net.URLClassLoader.findClass(URLClassLoader.java:347) ~[?:1.7.0_121]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:101) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:86) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
at java.lang.ClassLoader.loadClass(ClassLoader.java:425) ~[?:1.7.0_121]
at java.lang.ClassLoader.loadClass(ClassLoader.java:358) ~[?:1.7.0_121]
at java.lang.Class.forName0(Native Method) ~[?:1.7.0_121]
at java.lang.Class.forName(Class.java:278) ~[?:1.7.0_121]
at org.bukkit.plugin.java.PluginClassLoader.(PluginClassLoader.java:64) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
... 6 more
[15:54:35 INFO]: [INFO][NoCheatPlus] Tue Jun 06 15:54:35 EDT 2017
[15:54:35 INFO]: Player instances are stored for efficiency.
[15:54:36 INFO]: [Citizens] Loading Citizens v2.0.16-SNAPSHOT (build 1267)
[15:54:36 INFO]: [MOTDColor] Loading MOTDColor v0.5
[15:54:36 INFO]: [InWartung] Loading InWartung v1.2
[15:54:36 INFO]: [ProtocolLib] Loading ProtocolLib v4.2.0
[15:54:36 WARN]: [ProtocolLib] Detected outdated Java version: Java 7
[15:54:36 WARN]: [ProtocolLib] It is recommended that you update to Java 8 as soon as possible.
[15:54:36 WARN]: [ProtocolLib] Future versions of ProtocolLib many not support Java 7.
[15:54:36 WARN]: [ProtocolLib] Java 8 will allow for much faster reflection performance.
[15:54:36 INFO]: [WorldEdit] Loading WorldEdit v6.1.5;4651611
[15:54:36 INFO]: [PermissionsEx] Loading PermissionsEx v1.23.4
[15:54:36 INFO]: [Multiverse-Core] Loading Multiverse-Core v2.5-b719
[15:54:36 INFO]: [HolographicDisplays] Loading HolographicDisplays v2.2.5
[15:54:36 INFO]: [WorldGuard] Loading WorldGuard v6.1