If the outgoing and incoming calls don't succeed any more after upgrading Nokia N97 to version 20.x.019 (e.g. "Call not allowed" error shown), check the following things:

  1. Check that the SIM card is inserted in the device and that the device gets connected to operator network.
  2. Check that Offline profile is not in use. Change the profile by tapping the profile name on the home screen.
  3. Reboot the device.

If not yet working, reset the device in the following way:

  1. Take a backup of the phone contents for example with Ovi Suite or PC Suite.
  2. Reset the device with keypad command *#7370#
  3. Restore the backup but uncheck the Settings option.

Note that the reset command will wipe out the user data and you need to take a backup to preserve your data, or synchronise the data with Ovi Suite / PC Suite. When restoring the backup, the Settings option must be unchecked, otherwise the problem may reappear. If the problem still persists after restoring from the backup, reset the device again and use Ovi Suite / PC Suite sync to restore the data in your device.

The issue is related to version 20.x.019 and should not occur when upgrading to version 21.x.045 or later.