No lights at all? Not even the lights on the rear Ethernet port?
If there are no lights on the Ethernet port, it would suggest the Ethernet connection is dead (MyCloud port, cable, or router port). But then you would not be able to access pictures via iPad and mobile phone.
Are you really able to access pictures, or are you seeing thumbnails stored on the phone? Check by opening up a picture to full screen.
If you really are able to access pictures via mobile phone, then the device is still connected to the network, and the hard disk is intact, and the device is basically working. In which case, you need to find out why you cannot connect via your computer.
Have you recently upgraded the operating system on your computer?
What computer are you using?
Have you made any changes to your network? New router? New devices on the router?
Can you connect to the MyCloud’s Dashboard?
Can you find the IP address allocated to your MyCloud? Use your router’s admin page.
If you can find the IP address, can you access the Dashboard using that IP address?