There are 2 things preventing you from being able to upload videos over 15 minutes:

#1)  Content ID Claims are not in good standing.  To fix you must delete all videos that are blocked globally.

#2)  As long as you have any Copyright Strikes you won't be able to upload videos over 15 minutes.  If you receive no additional copyright strikes for the next 6 months then 1 copyright strike may (ie might) be forgiven.