The TS-4710, TS-4712, and TS-4720 are versatile system-on-module devices that can be used with a fair number of different baseboards designed and supplied by Technologic Systems and other companies.
The default image provided by Technologic Systems attempts to account for the majority of these baseboards and configure the SOM appropriately for the detected baseboard it is attached to, however, the software does not know about all possible baseboards. Some were introduced after the image maturity date (when we lock the software image to prevent damaging downstream production processes), and of course there exists custom hardware that was not designed by Technologic Systems.
The default FPGA includes the correct programming, so all that is needed to bring the CAN0 device into existence is to load the driver thus:
modprobe sja1000_isa mem=0x81004c00 irq=65 clk=24000000
From this point, starting SocketCAN will work as it's documented in the product manuals: