I can't generate gerber in Orcad 17.4

[rmaurisset]

Hi,

I am trying to generate the artwork files of my pcb layout on Orcad 17.4 and I get the error "Database has errors, artwork generation canceled. Please run dbdoctor".

After I run the dbdoctor, I get the messages below. Two errors were detected and fixed. So, I try one more time to generate the artwork, and I get the same error message
stating that I need to run dbdoctor.

ERROR: Detected subclass TOP is a zone surface but not identified in design.
Error was fixed.
ERROR: Detected subclass TOP is a zone surface but not identified in design.
Error was fixed.
0 warnings, 2 errors detected, 2 errors fixed.

Does anyone happens to know what could be creating this error?

Thanks,
Ramon