In Bright 8.2 and later, you may either:
* use categories and attach the slurmclient role
* use configuration overlays and assign the slurm client role.
The cm-wlm-setup wizard by default configures the slurmclient role under the configuration overlay. That is likely why the commands aren't succeeding under the category.
You can try:
% use slurm-client
% use slurmclient
You should now be able to configure the GRES resources.