Not accepting incoming network connections

I'm running 2.5.2 on a 2007 iMac running Yosemite 10.11.3. Ever since updating to 2.5.2, I receive the message "Do you want the application "Plex Media Server.app" to accept incoming network connections?" every time I boot. The Plex server is unavailable until I do so. I have verified that the Plex app is listed as "allowed" in my firewall exceptions settings, and have even removed and relisted it there. My iMac is set to automatically turn off at midnight and turn back on at 6am every day, so this can be frustrating if I'm not around when it boots.