[CA] AXIOM Pro Micro SD Cards

I have an AXIOM Pro 12 RVX unit installed in my system and have a question about Micro SD card compatibility.

The existing Navionics Platinum+ Chart Micro SD is a SDSC 8 GB chip in slot 1 (upper slot). I put a SanDisk Micro SDXC 64GB in Slot 2 (for video recording and snapshots) but the AXIOM camera configuration menu said Slot 2 was (empty). I powered off the AXIOM, reversed the two chips, powerd on, confirmed the Nav Charts worked, and checked the camera configuration menu. Now it said Slot 1 (the slot with with SDXC chip) was empty.

The Lighthouse 3 manual says the SDXC should be compatible but I am thinking maybe not?? Please clarify.

Thanks,

Jon