Is your phone connected to a work email account or anything like that? They can sometimes define policies that are applied to your phone as a condition of being able to access the work email system - for example they may be able to "wipe" your phone remotely from the email system should you lose it. Restricting Google+ might be a part of the restrictions being applied.
Hi Mat, I had 3 accounts on google one gmail & two with my virgin e-mail addresses. I have removed the main one but now when I try to access google+ I am directed to my virgin log on page. When I put in user name & password I get a page not available screen from google. I am now not able to access google + at all thru the app. alec