Do you have your access card with you at the moment?
If so Do this 
We can give you a much more targetted answer.
Do you know how to scan your card with your phone?
Install TagInfo and running - Remove phone cover - NFC ON -Screen on and unlocked - Move your card slowing on the back of your phone ( Top edge for iPhone ) - Then
Hide / change / remove your ID for security.
This may also help at some stage
WIKI - NFC phone performance - #95 by parvusvox
IF this doesn’t work ( Actully probably better for you if it doesn’t ) you likely have a Low Frequency card, this is a better “do it yourself” option.
To further confirm, next time you are at your work, Use your Diagnostic card ( Would have been included with your NExT ) on your readers, LF , HF or BOTH may light up.
When it comes to using your NExT on the reader, that’s when you will use your xFD ( key rings included in your package ) to find the sweet spot
Like I say with more info, the more we can specifically rather than generically help you.
I hope that all makes sense, Just ask if not, somebody will be along shortly to answer your questions 
OH, and
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