Hi Giulio,
Thank you for contacting us, and I'm sorry for the issue you are experiencing. Unfortunately, I don't know what you mean when you say everything worked when you had a free concact. I checked your account, and you have an Essentials subscription, so you should have no problems using Face ID.
I'm going to have you check your account real quick in the mSecure app on your iOS device. Go ahead and open mSecure, tap the menu icon in the top left, then tap Settings. In the Settings screen, tap Account Settings. Does it say you have an Essentials account?
Giulio