No this is not a server issue. It has to do with the web guard that is on all prepaid and some contract sidekicks. Call T-Mobile and ask to have the web guard removed.
note: To do so you must be the account holder of record and over 18. They will ask for your drivers license number to verify age. It takes about three days for the information to be confirmed and the guard removed. Even then it is sometimes necessary to visit a T-Mobile branded store and have them remove it there (again you will need to show ID).