The duoprox cards have two technologies in them. It is possible that even if you clone the 125khz side of the card, the readers are using the 13.56 mhz side of the card so it won’t do you any good. You know which side they are using?
Have you tried scanning the card with an NFC enabled phone and an app like Taginfo or NFC Tools?
Also if you have the DT Diagnostic card, you may be able to tell which tech they are using by using the card on the readers. Sometimes they use duoprox cards but use readers that only read one of the card’s techs so you know which they are using… If your readers are only 125khz, then I believe it should be clonable. Don’t quote me on that.
I’m not familiar enough with them to know if that’s possible. The DT Diagnostic card is your best bet but there is no all-in-one solution to your issue. It’s a matter of testing the card and the reader…and you need equipment for both.