Thats minecraft server life, please try rebooting again before panicking, then use pastebin or github to provide logs to the team for help diagnosing.

This is common on fresh worlds, or busy worlds when somebody does a significant action that takes the server longer than 60 seconds to process. Change max-tick-time in server.properties to 600000 (10 minutes) as a first step in getting past this. If crashes persist (they'll be a different error or take 10 minutes) then pastebin logs for help.

Edit \config\ftbbackups-common.toml while the server is OFFLINE, save it, then start the server.

Edit \world\serverconfig\ftbessentials.snbt (ftbessentials-server.toml for pre 1.7.x packs) while the server is OFFLINE, save it, then start the server.

This is a local environment issue. Usernames with spaces and/or incorrect java installed or set in the path/launcher youre using, frequently cause this. Get a good launcher that lets you install forge easily (like MultiMC), and make sure thats installed properly. Read the logs, and pastebin them for help if youre still broken.