Q: iphone 6 won't sync computer not authorized.  Have tried all of the fixes and nothing has worked

My work has updated my phone from the 5 to the 6.  I have multiple apps on it from different users because it is a work phone.  Now using my ITunes ID, I cannot sync with the iTunes.  It says that my computer is not authorized.  However, the computer is authorized.  I have tried the fixes that were posted and no luck.  Not understanding why this is going on as my previous iPhone had no problems and my iPad is able to do this as well.  Help!!!