This is less of a wishlist and more of a "fix"thread these days
There were two steps: (1) update (2) reformat. The order of those is important. You only mentioned #1. Did you do both?
If in doubt about #2 I would reformat the card to an entirely different system--maybe use your digital camera or something--and then force a tascam reformat, to be sure.
For what it's worth, I am using the 256G version of that card on my T12, no problems yet. And of course it's always possible you just got a bum card, for the low price of a 16G I would maybe try that out too.
Yes, of course I reformatted. It's not a bum card since it always worked with no problem on my Mac. But I haven't tried formatting in a camera. Somehow I suspect it will make no difference, but I'll try it anyway and report back...
This item in my "wishlist" is mainly that their officially supported cards worked. But better support for more types would be even better. I came from an old Zoom R16 that could record on any card I put in it.