People viewing your secured content – in Vitrium terms, are called the “Users”, “End Users” or “Readers”. When you send out a file and establish permission for individual users, only you can determine the authenticity of a user's credential attempting to access a secured file.
The majority of end-user issues will be related to incorrect username and/or password combinations, not opening the file with the correct program (i.e. the protected PDF file needs to be opened in Adobe), reaching their limit (i.e. in which case you could clear their use or reset their DRM policy limit), the file has expired or has been de-activated, or the user itself has been de-activated.
You should be able to handle about 99% of these issues if you have received training from Vitrium, read through this entire document, and have tested the program thoroughly.
If, however, you have exhausted all efforts to support the user, then you may request assistance from Vitrium by sending an email to firstname.lastname@example.org or by submitting a ticket through the Help tab in your Vitrium account.