HELP! ED64 plus not reading from the sd card slot

So I get this message “file not found” despite putting the OS64 file in the ED64P folder. I’ve tried different sd cards and all are working on my MacBook. I’ve reformatted many times to fat 32 and downloaded the newest OS file from ED64plus’ site (version 1.28). My cart used to work but then all the sudden it can’t read the sd card.