Error during IBAN creation
Variant 20 Bank area not in table TBKK01; Bank key cannot beread.
Variant 21 Country key not found in table T005 (country table).
Variant 22 Error during IBAN creation using new procedure (FI)
Variant 23 Error during IBAN creation using old procedure/TBKK06
Variant 24 IBAN is already in table BKK42

Solution
Variant 20 Customizing/bank area
Variant 21 Customizing/country
Variant 22 Customizing/in country table (country/rules) or banknumber directory or BTE 00003030
Variant 23 Customizing/create BKK_IBAN_CREATE_BBAN_US
Variant 24 Assign different account number.