Your mod crashes the server.
Error from the log:
07.09 19:59:54 [Server] Server thread/ERROR [FML]: Caught exception from mhfc (java.lang.NoClassDefFoundError: com/mojang/realmsclient/gui/ChatFormatting)
07.09 19:59:54 [Server] Server thread/ERROR [FML]: A fatal exception occurred during the server starting event
(Let me know if you need the full log)
Seems like people have posted a similar problem but the issue definitely is not fixed and this is the mod from the "Official Download" on the first post of this thread. If you've got a fix please upload it to the first post or reply so that we can use it on our server. Thanks!