A few weeks ago I was having this issue. I was told to run the Database Optimize, Clean Bundles, and Empty Trash then restart Plex. At the time it worked. It is happening again and this has not resolved the issue this time.
Plex Version 1.13.2.5154
Synology DS415+ Running DSM 6.2-23739
I am forwarding Port 32400 to my NAS via my Router. and Technically it all still works, Plex is just telling me that all connections are Indirect if you are not on my local network.
I have attached the Plex Log below.