Hello,
I have a 128Gb Samsung micro sd card and it works without problems.
Please make sure that you plug your micro sd card when the tablet is off and if that doesn’t help try changing to another version of the BIOS (the version that comes with the tablets shipped these days should be good, I didn’t need to change my BIOS version).
Another thing that I read in the past is formatting the card to ExFAT and then plug it into the tablet and see if it can be read then.
Hope your problem gets solved!