This thread is a bit old, but I had the same problem and just found a solution. It's related to this this thread.
When you activated Matlab, you specified your administrator account. As a result, the license file is saved to the administrator account, not your user account. Every time you start Matlab, it can't find a license file and starts the Matlab Activator (which requires administrator privileges).
To solve this problem, activate Matlab and when prompted to put in the account name, replace the administrator account name with your user account.