Mate, I really dislike A LOT of things about apple 
, but even though their tech is at least 2 years behind EVERYBODY else, it still does work.
If it was the spark original or xSLX I would understand.
Can you confirm It works with apple pay (should work easily with an active reader)
What App are you using? (sorry if I missed it above)
Have you tried TagInfo by NXP (the people that make the chips, so probably your best bet)
Also NFCTools might be worth a try
Also, have you read through this? there may be some more clues /hints for you to try