Hi Ganesh,
We encountered a similar issue in our implementation.
In our case, the sync expression was returning a Record Type reference instead of a Map/List (CDT or Dictionary). For service-backed records, the sync expression must return a list of maps/dictionaries or CDTs, with the primary key field populated for every row.
Although the data was visible in Data Preview (since it reflects the direct integration response), it was not appearing in a!recordData() grids or the default record list view because the sync expression output structure was not valid.
After updating the sync expression to return a properly structured map/list and ensuring the identifier field was populated correctly, the synced data started reflecting in:
Record Data Preview
a!recordData() grids
Default record list view
It may help to validate the return structure of the sync expression and confirm that it aligns with the record’s primary key configuration.
Hope this helps.