To see USB.Network drives, ST must boot with CosmosEx driver. That happens when you have no SD card plugged in, as there is no other possibility. When you have your SD card plugged in, it all depends on your configuration settings. Most likely you configured your card in RAW mode as ACSI 0 device, so ST boots directly from card without any CosmosEx drivers, so USB/Network drives (in Translated mode) are not visible.
Atari: Falcon030 + CT60 + SuperVidel + SvEthlana, TT, 520ST + 4MB ST RAM + 8MB TT RAM + CosmosEx + SC1435, 1040STFM + UltraSatan + SM124, 1040STE 4MB ST RAM + 8MB TT RAM + CosmosEx + NetUSBee + SM144 + SC1224, 65XE + U1MB + VBXE + SIDE2, Jaguar, Lynx II, 2 x Portfolio (HPC-006)
Adam Klobukowski [firstname.lastname@example.org]