In August 2020, COMFILE Technology began transitioning from the Compute Module 3 Lite (CM3L) to the Compute Module 3+ Lite (CM3+L). If you are using an older operating system image (e.g. Raspbian Jessie) with a newer ComfilePi panel PC that has a CM3+L, it may not boot because the operating system image does not contain the latest Raspberry Pi firmware. The preferred solution to this is to update the operating system, but if that is not feasible, please use the following procedure to update the Raspberry Pi firmware on an older operating system image.
sudo apt update followed by
sudo apt install rpi-update to install the rpi-update utility.
sudo rpi-update to run the utility, and follow the onscreen instructions.