The multiple volume feature works with USB3 host with UASP support only. If your host is USB3 type A port, please make sure your adapter cable is usb3 compatible. Most of these USBC to USBA adapters support USB2 only. USB can see 4 volumes with LUN0/ID0 to LUN3/ID0 only.
Tags: ARC-8050T3U, USB 3.0