Is your Gen 7 too updated to 5644 ?
Currently have a baremetal Gen7, 5.2-5592, but I can't install 5592 update 4 anymore since 5644 is available.
So I'm wondering about direct update my Gen7 to 5644 from Setting Panel.
Yes my gen7 is updated to 5644. According to others' posts it should work just fine. It seems that only the gen8 is having a problem.
Something in the gen8 hardware or bios is causing it to reboot right after xpenoboot finishes loading. It may be a matter of turning off settings or disabling things in the gen8 bios to get 5644 to boot but the family needs their plex server.