First sorry for the wait, I tend to give some daily attention to FreeNAS/FreeBSD topics, but I’ve been away a few days, hopefully I can help you guys now.
Manually trying to run the binary will not work, we provide a start.sh script in our tarball, but it seems this is removed by the port , but perhaps logs are enough 
I can’t seem to repo the issue with this version, It starts fine for me, can any of you post the last PMS logs after they attempt to start?
It should be in /usr/local/plexdata/Plex Media Server/Logs/Plex Media Server.log (or /usr/local/plexdata-plexpass/Plex Media Server/Logs/Plex Media Server.log depending where you installed/ which port flavor you’re using.
Also FYI, pkgng keeps older versions of the txz in the cache dir unless you wipe it, look in var/cache/pkg/ and you should be able to roolback using pkg install PATH_TO_TXZ
