Well, write here what the SIM is displaying and we translate it for you
wco81, did you register the sim on the Poste Web Portal?
PosteMobile , attention that's in italian.
Anyway you can try to write an email to
info@postemobile.it , if you bought the simcard last May you can use it until Aprile (they have a validity = 11 months + 1).
PS: I had "simcard rejected" on locked phones too.