Hi there.
i have the same trouble like some (many) other users with emby and my synology nas. no connection to internet (serverside)
check for application update failed
check for plugin update failed
no metadata download
no plugins for installation visible
all connection to internet from (emby) serverside are stuck
connection to internet from (synology) serverside runs fine
my configuration:
synology ds413j
dsm-version 6.2.3-