Server is unavailable



I am using western digital's 'My Cloud Home NAS'. I have enabled plex media service on my NAS, and configured the server on Plex account. It was working fine and I was able to stream my media content from my NAS to all my devices. But once I restated the NAS, plex was unable to find the server, and a message comes: > "The server "XYZ" is unreachable. Make sure it's running, double check your network, and try again." Though my I am able to access my NAS content directly.

To make it work again I have to disable the plex media service on my NAS and re-enable it. After doing so a message appears on the Plex page- > "An insecure media server has been found on your network. Reload app insecurely". Once I reload the page my server is found back, but only for few hours. After that I have to repeat the same step and thus I am stuck in the loop.
Kindly help me out of this, as every time I repeat this process, plex prepares the library from scratch, so I have to wait for another half an hour to use plex before my library is fully updated.