There are two different scenarios and please closely check which one applies to you.
- The error message reads: Security code has not been set. Please set security code. In this case your phone is asking you to enter a brand new code. So, don’t use your old security code but create a new one.
- The error message reads Code error and you try to unlock it with your old correct security code but still the same error message comes up or states Phone will unblock in 5 minutes. In this case, despite the error messages you can still use your phone. Please try to enter your existing security code a few times until the phone stops asking for it.
If all that doesn’t help, please visit your local Nokia Care point (locations are visible via www.nokia.com/support).