In this post, there is indication that you might get this error message because the NAS tries to access the firmware server and uses this test to determine Internet Access.
Is the rest of the NAS functionality working fine (local access, remote access)?
How is your My Cloud connected, is it to your router? What shows under Settings>General>Cloud Access? Does it show connected? How about Cloud Access under the General setting.
Below is what shows in my Dashboard for Settings>Network.