Resolution:
This happens, when the custom opcodes are not imported properly ( the memory mapped extension file for the opcode is not found). When importing custom opcodes, the following needs to be taken care of:

1. Make sure that the memory mapped extension file is placed in the bin folder of the adapter installation
2. The pin.conf should have reference to this extension file's location (the absolute path of this extension file should be gven in the pin.conf file  )
3. The pin.conf should be present in the folder where the html I/O specification files of the Opcode is kept.
4. The Opcode should be re-imported. (Ensure that the pin.conf is places in the same directory as the html files, or rather the best option would be to place the html files in the Bin directory of adapter installation itself.)
5.After importing the Custom Opcode, the extended property for the custom fields should be verified against the field ids assigned as part of the header file used while creating the memory mapped extension file.

Why does the Field Ids for fields in Custom Opcodes show up as "0"?