You are on the Accounts Details page and the page keeps telling you that "Your VPN account username looks like this my_identifier@invizbox" as in the image below:
This is most likely due to a couple of characters having been badly entered.
In the example above, the user entered an % symbol instead of an @ symbol before the invizbox.
Note - For users who purchased before October 2017:
Our VPN usernames used to be generated from your email address and this lead to confusion when typing them in. The most likely typo was that the @ symbol (at) from your email address would have been replaced by an _ symbol (underscore) in the VPN username.
For example, a username would have looked like "myname_gmail.com@invizbox". You can notice that the _ instead of @ before gmail.com.