Drobo 5N has no MAC address

Hi, my Drobo 5N is attached to my iMac via tp-link TL-SG108 E Easy Smart Switch and I can see the IP address but the MAC address is “UNKNOWN”.

I can connect to it via Finder and see the files, etc but the Drobo Dashboard is unable to connect and I am also unable to ping it.

Is this because of the switch?