NHC in MX915 is not working

Hi,

We are implementing contactless payment in our box office and the NHC feature is not working in the credit card terminals. We made the change in the config file to TRUE for <iscontactlessEMVallowed> and we also installed TriPOS 5.17 in the workstation but it still showing just two options insert or swipe a credit card. 

Please advise.