#1 does it show up as something you can format under storage options? #2 does it show up on your PC when plugged in an adapter? My 64gb evo is fine but there are so many revisions for different markets I doubt it is the same.
From what others have posted on the forum, the S8s appear to be very finicky on what they'll accept for an SD card. I brought my 32gb over from the S7e and it's working okay but has had a couple burbles. One poster noted a mark on newer cards that mean it's approved by Samsung, but not sure that's a guarantee either.
There are also a couple other threads going on the same issue. See: