If you get a response saying Nyx can't do something due to role hierarchy, then Nyx's role is too low to perform an action on a member.
As said here, users cannot ban / kick anyone with the same role or a role higher than theirs.
Fixing this is easy; all you have to do is drag Nyx's role above the other roles in the server settings.
Go to your Discord server settings, find the roles tab on the left side and click on that.
Find Nyx's role, and drag that above the other roles.
Make sure to save the changes made.
If the problem persists, or another error shows up after doing this, please join the support server.