Docs
This article covers the instructions to resolve the sync error
Error: There's a problem with this state, even though it may appear correct. Please select a state from the list of valid states.: Mailing State/Province:MailingState –
Summary:
Chargebee uses the ISO 3166 alpha 2 format of country code. Example: Places such as Puerto Rico, Hong Kong are states under countries United States and China respectively. Due to this mismatch, the error mentioned above are thrown during the sync. States list is picked from the ISO 3166 alpha 2 format of country code. Salesforce uses a different format and hence the mismatch.
Solution:
Update the state names such as Hong Kong, Puerto Rico, American Samoa, U.S. Virgin Islands, Guam, United States Minor Outlying Islands as country names in Salesforce country picklist.
Here is a help document from Salesforce on updating the picklist.
Articles & FAQ