I have PERM and I-140 approved and employer filed H1B 6th year extension based on I-140 but received RFE. Don't know the reason yet bu here;s my case.

1) My Qualification is Bsc (Zoology) + 2 yrs Software Development Diploma from New Zealand + C-DAC (2 yrs part time)
2) Total IT experience 15+ years

What do you think what could be the reason for RFE? What are my chances of getting the approval? Any issues with my qualification given that more work ex?