Made the 2-hour trip one more time. With factory reset phone, 64GB, and 128GB microSDs in hand.
Employee confirmed that the phone "appeared to have been reset". So we reset it again.
And tried the 64GB card. No go, again.
And tried the 128GB card. No go, again.
Two employees were able to mount both cards in their phones with no problems (ruling out bad cards).
Tried to mount a new 64GB card off the rack. No go. Employee was able to mount the card in his phone to rule out a bad card.
Got tech support on the phone. And they reviewed all the notes thus far.
Their first opinion: Bad cards.
When we reminded them that all three cards mounted successfully on other S5s, we were instructed to factory reset the phone again.
We did. None of the cards would mount.
Tech support's response: We need to go to another store and buy another card. Just to be sure we did not have three bad cards(!).
Definition of insanity: Doing the same thing over and over while expecting a different result.
Definition of arrogance: Requiring someone to do the same thing over and over and telling them the results will be different.
At this point I would just play the game, pop over to another shop and prove that it's not the cards, the notes should be current, unfortunately they've deemed this a valid excuse not to swap your phone, I personally find this quite odd.
One brand new card should not be defective, especially if it works in a different handset.
Feel for you mate, but you've got to play the game at this point.