Try rebooting your PC/Mac (shutdown all other PCs/Macs too that may be accessing the 5N too if you are able), close all applications on start up.
Login as an Admin user if not already and attempt the deletion again?
Nothing has worked. I have restarted the Drobo, the workstation, and the router. The Drobo isn’t mounted on startup. I am always in Admin. I have attempted this several times.