If I install a plugin for my server, can a reseller utilize this plugin as their user?
Some plugins, such as cPGuard, require UID 0 access (root) and will not allow access for the plugin. Other plugins such as CSF need you to enable this for a reseller. Munin allows this if you enable the "All" ACL. JetBackup allows this within the Permissions Tab. Please review the documentation for your specific plugins and verify you have the Reseller ACLs adequately configured. You can do this through the Edit Reseller Nameservers and privileges section of the WHM.