Dear Abhinav,
I forgot that BModes doesn’t like flp_iner and edge_iner to be exactly zero; BModes won’t complain, but it won’t deliver the correct results either. I’ve modified my forum post above to clarify this. A similar discussion took place in the following forum topic: Tower Eigenfrequencies of NREL 5MW Turbine.
I also noticed that you have tower draft (draft and ref_msl) set to 20 m in your BModes input file. If its not, you want this value to be equivalent to the platform reference point in FAST v7 (or in ElastoDyn module of FAST v8).
Best regards,