Caused by: java.lang.NoSuchFieldError: END_PORTAL_FRAME
at com.onarandombox.MultiverseCore.listeners.MVPortalListener.portalForm(MVPortalListener.java:74) ~[?:?]
at sun.reflect.GeneratedMethodAccessor267.invoke(Unknown Source) ~[?:?]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_192]
at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_192]
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]

Can you provide us with more details, such as the full console errors, as well as bother the mv plugins versions and your server version. Thanks!

Closing this due to the lack of information.

For 1.8 server, you will need to use an older version of Multiverse - 2.5 should work (not the same as 2.5.0): https://dev.bukkit.org/projects/multiverse-core/files/898527

for sign portals: https://dev.bukkit.org/projects/multiverse-signportals/files/772770