Hi Prasad
Can you share the external database table and its properties
Also share the full insert query
This is a known issue in the Mendix 10.11 version.
If you need to use the insert query in the same version then install Database Connector version 6.0.3 from Marketplace Module and use the Execute Statement java action in the microflow.
Create a string variable and update the query string inside the variable in below format
'INSERT INTO SAMPLE_TABLE ( COL1, COL2 ) VALUES ( ''' + $COL1 + ''', ''' + $COL2 + ''' )'
Then execute this statement and this will work.
Hope this works