I am disappointed in WD and not happy that I bought a MyCloud from them. I bought a 4TB MyCloud a few years ago so I would always be able to backup my photos, videos, and important documents. It was amazing when I first got it- it worked flawlessly. Then, as everyone knows, rather than just patching security holes, they disabled remote access and are trying to force everyone to buy a new one- lame! Now, it is not only disabled for remote access, but I cannot access my files when I am at home on the same network from my PC or my iPhone app. Nothing changed except WD MyCloud is telling me I cannot access it. I understand the need to increase revenue for the company, but disabling rather than just simply patching the older network drives is unethical. At the very least, I need help accessing my files while on the same network so I can move them off of the drive. Any suggestions would be appreciated.
Can you access the My Cloud Dashboard?
My Cloud OS 3: Access the Dashboard on a (single bay) My Cloud
https://support-en.wd.com/app/answers/detailweb/a_id/15104
What color is the front LED? Blue or some other color?
For the iPhone you will need to use a file manager app from the Apple app store. And that iPhone will need to be connected via WiFi to the same local network as the My Cloud.
For your computer, without more information we can only guess what your issue is. If using Windows ensure SMB 1.0/CIFS is enabled. If using Mac make sure to connect to the My Cloud using SMB as Apple has depreciated AFP.
My Cloud OS 5, Home & My Passport Wireless: Enable SMB 1.0/CIFS File Sharing Support on Windows 10 & 11
https://support-en.wd.com/app/answers/detailweb/a_id/4155
My Cloud OS 5: macOS Time Machine “Backup Disk Not Available” or Finder “Connection Error”
https://support-en.wd.com/app/answers/detailweb/a_id/32003
Windows: Map a WD Network Drive on Windows 10 & 11
https://support-en.wd.com/app/answers/detailweb/a_id/25436
My Cloud & My Cloud Home: Map Network Drive on macOS
https://support-en.wd.com/app/answers/detailweb/a_id/24148
No issues with local network access on Windows or on Android (using a file manager app) accessing a local network v4.x single bay first gen My Cloud.
Image below shows both of my WD My Clouds, a 1st generation and a 2nd generation. I am still using both and have access to both. The 1st generation is local only. The 2nd generation, OS5, has remote access. Click on, tap, or activate image to enlarge it.
Well. . .SOMETHING must have changed 
I have multiple NAS’s running the “obsolete and insecure” OS/3. Other the losing the cloud apps; and isolating them from the internet. . . nothing has changed in the operation of these old boxes.
Most likely culprits are a change in the IP address of the device; OR the SMB1.0 issue Bennor mentions.
The OS3 MyCloud app no longer works. You need to access your files with windows explorer or Network explorer.
