1030 no longer reading OS maps from SD card

Hi Folks

I could really do with some help with my Garmin 1030. My Garmin has stopped processing the OS maps from the SD card.
I have factory rest my unit.
I have borrowed a friemds Garmin 1030. His reads the card with no issue. When I put his card in mine, mine does not…. Very confusing. can any one shed a light on this please? Both are at the same software build
Thanks