I also don't know why this would cause the volume to not appear at all in the Intel RST software -- that seems like a bug.
This is expected behavior, the software will not be able to make use of the RAID volume since the BIOS was not set to RAID.
So I don't know what the original "Your system is reporting one or more events, and data may be at risk" was about.
I did not find any information regarding this message but it seems that the software did not like having this RAID volume together with the AHCI mode.
Anyway, it is great that you got it running.