You can now use permission-based rankups. Instead of players needing to be in a group, they can now just have the permission (for example) rankup.rank.member. If this system is enabled, Rankup won't automatically do anything when a player ranks up and you will need to use commands to give them permission for the next group.

The option in config.yml is permission-rankup (you may need to rename or delete your config file to generate this option).

Example config: https://pastie.io/ohlmuh.yml