I use Samsung 32GB class 10 and it works very well on Android 6 or Android 7 after update.

I just got mine working on the BV6000S.
I put it in the BV6000 and the other card (Sandisk) that was in the BV6000 I put into the 6000s and then connected both to the computer. I deleted all the files on the Verbatim and copied over the files from the Sandisk to it. Now when I put the Verbatim in the BV6000S it runs fine.

For me, this must really come from the sd card reader
because I did exactly like you hood, but that does not work.
And even by formatting them completely with my pc,
the bv6000 no longer detects SD cards.

If it"s hardware problem of sdcard reader there is nothing easy to do ...
If it's software problem, maybe you could try to flash again your current ROM. This process help me many times for various bugs !

With all the bugs of the update, I will not do it and wait a
month or two to redeem myself a phone and no Blackview.
But thank you even for your help.