Did you set up a boot flag on first Virtual Drive after creation of second? The LSI WebBIOS is kinda tricky: by default none of Virtual Drives have that flag, and if there is only one VD, controller deal with boot, but if there two or more, system may not boot, even in non-EFI environments.
From the WebBIOS main menu, click the Virtual Drives - double click your first, select 'Set Boot Drive' (make sure right VD is highlighted above), press 'Go' button, then accept changes.
JFFulcrum, thank you for taking the time to help troubleshoot my problem.
I did notice the boot flag option in the LSI WebBIOS. With both virtual drives present, I have tried with it set and unset. Unfortunately, changing the option doesn’t appear to change the behavior. So far, the only way I’ve seen this system boot with UEFI is when the card is only presenting one LUN.
I have no data on these drives, so I’m in a situation where I’m able to completely reset the configuration and reconfigure without a problem. If you have any other troubleshooting ideas for me, please let me know.