Help needed with a server error!

I was trying to promote a player on my server after just recently adding some permissions to that group to see if they work and I type /manpromote name player and it gave me this error:

[WARNING] Unexpected exception while parsing console command org.bukkit.command.CommandException: Unhandled exception executing command 'manpromote' in plugin GroupManager v1.9 <2.9.1> <Phoenix>

And then it continues on with a bunch more console things. Any help will be EXTREMELY helpful and appreciated.