Please check that bluetooth is enabled in app settings. The app asks for bluetooth permissions when you first install. If you have accidentally clicked 'No' - the app won't function by presenting it to a card reader point. To check this on iOS for example:

Go to you phone's 'Settings'

Scroll down the bottom to 'App's

Search for or scroll down to 5dkey

Check that bluetooth option is enabled. 

Still not working? 

You can try to manually authenticate, by pressing the virtual card entry for 3 x seconds. This will force authenticate, and will provide feedback, i.e. bluetooth not enabled if there is an issue. Another reason may be you do not have back end permission in the access control system for the door you are trying to access. So if the reader beeps, and you get an app 'success' pop up, this is a possible cause, please see a site access control admin to check.