Hi,
In general, a DVI monitor could stay blank after powering on a device because of BIOS settings (e.g. if the APC has additionally a SDL4 display output, and the BIOS is set to use that interface only), but it’s also possible that the system “stucks” after power-on in the POST (Power On Self Test) because of a hardware failure or an unvalid firmware (for example after a broken firmware update).
So I only can recommend the same like in the other thread: please try first to remove all devices that are plugged into the system (CFast, PCI cards) and check if something changes to get more details about the possible cause.
If nothing changes, please contact your local B&R support team.
Just out of interest: what Operating Systems are used on the APCs? GPOS Systems (Windows, Linux) or Automation Runtime embedded?
Best regards!