If FAB 3000 has successfully extracted nets from the Gerber, those nets will definitely be there in the ODB++. To verify this try using the free ODB++ Viewer (provided by the ODB++ Alliance) and you should be able to easily query those nets: https://www.odb-sa.com/downloads/
1 If no nets are found while using the ODB+++ Alliance Viewer, please send us any sample Gerber and I'll be happy to create a tutorial showing how to generate and export nets in an ODB++ file.
2 If yes nets are found while using the ODB+++ Alliance Viewer, perhaps during parsing of the ODB++, your test program requires a specific table or other attribute to recognize nets? If this is the case we're happy to optionally include that table or attribute if we can better understand the issue.
Note: You can also import the ODB++ back into FAB 3000 to verify nets are actually included in the ODB++ file.
Either way we're happy to assist, and I look forward to hearing from you.
I already downloaded and tried the FAB 3000 trial and was able to import various gerbers and tried extracting the netlists from these. This did work up to a point, but when I saved it as ODB++ file I wasn’t able to find these netlists again in my test program.