Configure State or Country Code Mapping In Salesforce

State or Country Code mapping must be configured correctly in Salesforce to avoid integration errors. If there is any discrepancy between State or Country codes in Salesforce and NetSuite, the following error can occur.

Error Message: There's a problem with this state, even though it may appear correct. Please select a state from the list of valid states: Billing State/Province.

This problem occurred because NetSuite uses a two-letter ISO code to represent state and country codes, even if they appear as names in the customer or contact form (for example, California). 

To fix this issue, it is recommended to configure the Salesforce integration values, to use the two-letter ISO codes.
Follow the configuration steps:

1. In Salesforce, go to Setup. 
2. In the Quick Find / Search Box, enter 'state'.
3. Select State and Country/Territory Picklists.
4. Click Configure States, Countries, and Territories.
   
5. Click the Edit button of the country you want to modify the record.
   
6. Modify the Integration Value to a two-letter ISO code.
   For example: If you select the country “United States” then change the Integration Value to “US”.
   
7. Follow steps 5 and 6 for the state mapping.
8. Click Save.