The standard bank account format in NZ is 00-0000-0000000-00. The first segment is the bank, the second the branch, the third the account number and the last the account suffix.
As part of the account code there is a check digit which FlexiTime uses to check whether the bank account number is valid. If you've accidentally typed an incorrect number in the branch or account segments, FlexiTime will pick this up and you will need to check and correct the error.
Some accounts numbers from the old National Bank can cause problems. These bank accounts will start with 06, and the account code portion will typically have two zeros at the start. The problem is that the National Bank internet banking sometimes displays the third account code segment with an extra zero at the start. This can either result in an 8 digit account code or a three digit suffix. This extraneous zero will mean the bank account is considered invalid.
The solution is simply to remove the first zero in the account code. Doing this should mean the bank account correctly fits the standard 00-0000-0000000-00 format.