09-11-2011 5:38 - edited 19-12-2013 18:30
I've suffered from this problem (I have a 6300) and I have come across many similar situations. So here is a guide (Reasons & Solutions) to help you solve this problem.
1. Deleting the certificate manually from security settings.
2. Getting your phone flashed at an unauthorised repair shop. It is not recommended to do so for it voids the warranty, it deletes all the certificates from the phone and you may end up with a dead device.
1. Update your software using Firmware Over The Air (FOTA). If there is any update available, certificates will be sent on your phone - download & then install them.
2. Try reinstalling the firmware using Nokia Suite/Nokia PC Suite. It will install the genuine software for the phone and along with it the certificates will get installed.
3. If nothing works please contact an authorised Nokia Care Centre that is near you. You can find the location at Nokia Support.
For firmware reinstallation/update (Guide & Things to Remember)
Connect your phone to a computer & select Nokia Suite mode. If you do not have Nokia Suite on your pc you can download it from here. Now open the Nokia Suite & click on the “green icon of arrow pointing downwards”.
If any updates are available they will be shown in ‘green’. If not you may reinstall the current version. Reinstall option is shown in ‘blue’. If no option to reinstall is shown, please wait for sometime it will become visible. Then the Nokia Suite will download the new software version of the phone. After it you will be prompted to take a complete back up of the device content. Please do not skip this step as reinstallation will erase all the personal data from the phone like contacts, messages, calendar entries etc.
Please note that if you have set a memory card password & you have forgotten its code then take a backup of the card data also as the card will be locked after update and can only be unlocked if you enter the correct code or by ways mentioned in this thread.
Also note that while updating the device ensure the following things-
Also check out this video on YouTube with instructions for update.
Please note that the above solutions work for S40 phones. I am not sure about other platforms such as S60 etc.