Didn’t want to start a new topic but I am having the same issue as a lot of people. My Plex server has been working for over a year straight with no problems and just the other day BOOM! remote Access - Not available outside your network and the only change was an update.
What you did? Updated Plex
What happened? Lost access remotely
What are your (relevant) settings? Windows 10, Netgear Router, Fiber ISP
Feb 28, 2019 04:32:04.979 [0640] DEBUG - NAT: UPnP, public address is 10.151.96.109
Feb 28, 2019 04:32:04.979 [0640] DEBUG - PublicAddressManager: got WAN IP 10.151.96.109 from router
Feb 28, 2019 04:32:04.979 [0640] WARN - PublicAddressManager: WAN IP is a private IP address
Your logs show your public IP is being reported as a private IP. You might have some sort of double NAT issue going on.