Remember to fill in the attribute_category, when updating descriptive flexfields defined with context.
If you omit the attribute_category, the api will successed and database will be updated, but no value will be shown…
We just had a case where HZ_CUST_ACCOUNT_SITE_V2PUB.UPDATE_CUST_ACCT_SITE where completed successfully, but not value where shown and database was updated. We forgot to fill in the org_id in attribute_category and the DFF was setup with reference to $PROFILES$.ORG_ID.