Error message "Failed to create the first available code that matches the format" when creating a new account

This error message indicates that the auto-numbering of creditors/debtors is not configured correctly in Twinfield. Go in Twinfield to Settings / Administration settings / Dimension types and choose 'Creditors' or 'Debtors'. In 'Format', a format suitable for auto-numbering must be set. Consult the Twinfield manual for details. A valid format is for example: 2[0-9][0-9][0-9].