THAT is very strange
I looked it up, and it states
Additional info * RS485, Wiegand34/26 protocol(Default 34)
- 13.56MHz(Mifare)
- 125KHz(EM-ID)
Both frequencies, So your diagnostic card SHOULD have lit up 
, very strange.
Can you scan your genuine card/fob on the system and share the results that show up on Jablotron Security system?
This may help us to figure out the UID, so we can work out how many bits the UID has which may help us work out what chip we are working with. ( change some of the figures for your security )
FYI Your NExT should be by default in EM41xx with a 40 bit UID
Because it is a Dual frequency reader, Just so we can rule HF out, Can you try scanning your card with your phone with TAGInfo App.
When you scanned the Diagnostic card, was it very bright where you scanned it? 
Did you try scanning the diagnostic card on the reader and then place your access card on top of the diagnostic card, to see if it lit up when access was accepted.
Just in case the diagnostic card is broken, Do you have the Field detectors to try also?
If you can try those for now, and we will see what we can do next