You may be experiencing an issue after updating to El Capitan (Mac OS 10.11) when trying to view your NAS in Finder: it shows up as a question mark, or it just gives an error message when trying to connect to it. Below are instructions for connecting to a NAS from Mac OSX using a different method:
Note: On Seagate NAS Pro models with the LCD monitoring screen on the front, you can find its assigned IP address there instead of looking in the Arp table from Terminal (as described in the steps below). See this section of the Seagate NAS Pro user manual for more information. (Only applies to Seagate NAS Pro 4 and 6-bay models) - If you find the IP address with this method, or already know the IP address, skip to step 6 below.
Make sure you see ‘Finder’ in the top left corner of your screen (by clicking the desktop first) then click on Go, then Utilities.
Now choose Terminal.
The Terminal window will open. Type “arp -a” and then hit Enter.
You will see a list of IP and MAC addresses [ex. ? (192.168.1.23) at 0:10:75:44:DD:11]. Locate the Seagate NAS MAC address in the list.
Note: You can find the MAC address on the bottom, or backside of your Seagate NAS. All Seagate NAS units start with 00:10:75, however terminal will only display the first zero.
Once you have located the MAC address, look to the right and make note of the IP address associated with the MAC address.
Now that you have the IP address of the drive, make sure that you see Finder in the top left corner of your screen, then click on Go, then Connect to Server.
In the ‘Connect to Server’ window, type: cifs://IP Address or afp://IP Address (ex. cifs://192.168.1.85 or afp://192.168.1.85).
Note: Make sure you use a forward slash (/) and not a backslash (\) .
When prompted, enter your username and password and select Connect. The drive is now mapped and can be accessed under Finder > Shared
Note: By default, your Mac will auto-populate the username field with the Mac's username. Change this to the username of the account on the NAS you would like to access the NAS with.
If you do not see the NAS in Finder, check your desktop. If you do not see the NAS there, follow these steps:
Click on Finder in the top left hand corner of your screen.
Under the General tab make sure “Connected servers” is checked. This will allow the NAS to show up on your Desktop.
If you still can’t connect to the NAS, then your computer might not be connected to the correct network. Here are a few suggestions for what to try next:
Make sure the computer is connected to the same network as the NAS. Here is an example of how it should be hooked up: Your NAS is plugged into your router via Ethernet cable and your computer is connected via Ethernet or Wi-Fi to that router. Make sure you are not connected to a guest network. See Picture below for a visual aid:
If you still cannot access the NAS, check to see if another device (computer, TV, or Media Player) on your network can see it. If nothing on your network sees the NAS at all, then you should power cycle your network. Steps to power cycle your network are below:
First, unplug the Seagate NAS from power, and then from the router by unplugging the Ethernet cable. Once it's completely disconnected, turn off your computer, and then reboot your router.
Wait about two minutes after rebooting the router and then reconnect the Seagate NAS' Ethernet and power cables. Once the NAS is booted up (status LED has stopped blinking), turn your computer back on and look for the Seagate NAS again under Finder>Shared.