Short answer: If a NetSuite custom field's value is not stored on the record, Kolleno cannot read it. Make sure the field stores its value (rather than only displaying one dynamically) before expecting it to sync.
Why this happens
Kolleno reads NetSuite data via SuiteQL. SuiteQL can only return values that are actually persisted to a record's field in the database. Some custom fields in NetSuite are configured to display a value dynamically.
For example, sourcing a name from a related record at view time — without ever writing that value to the field itself. These dynamic-only fields return nothing in SuiteQL, so Kolleno has no value to pull.
How to fix it
Ask your NetSuite administrator or consultant to confirm that the custom field is configured to store its value on the record. In practice this usually means:
The field has a defined type and is saved on the record (not purely a formula or dynamic source that runs at display time).
Existing records have been updated so the field is populated; newly stored fields are typically empty on historical records until a save or mass update writes the value in.
Once the field stores its value, it will become available in SuiteQL and Kolleno will be able to read it on the next sync.