This is something I've just realized has been popping up for me for as long as I've been using armbian the past year or so with my ODROID.
After a clean setup, I use armbian-config to edit the network settings (ethernet connection) to a static IP address, and everything works fine. I reboot the changes and go on my way. The problem comes after I reboot days/weeks later for kernel updates or if I lost power. The board turns on fine but refuses to show up on my network and therefore cannot SSH to the system. Looking through the SD card and checking the files shows that /etc/network/interfaces is devoid of any static IP changes made through the config, although it looks like correct information is shown under /etc/NetworkManager/system-connections/Wired\ Connection\ 1.
The board light flashes a steady blue and seems to be functioning otherwise, but the logs don't really show anything after the reboot. I do have lines in /etc/fstab for filesystems that aren't present at boot, could the process be hanging on that? Is there even an easy way to debug this as it's not like I can plug in a monitor and see the boot messages?
Wired Connection - NetworkManager connection file
Auth log prior to reboot
Syslog reboot