VivoKey Apex Flex Not Working

Which model iPhone do you have?
Have you tried the top edge (where the NFC antenna should be)

Take your time, move very slowly.
The P71 chip is more advanced than most others you would be trying to read so it takes longer to read and write.

Also, the antenna of the Apex is a lot smaller so you need to be more precise than with a full sized card.

Let us know how you get on…