Attempt to insert object with the same key as an already existing object.

[#1]

Hi,
I'm trying to add a new subnet on InfoBlox and getting this error below.
"Attempt to insert object with the same key as an already existing object."

I couldn't find this subnet in the database. I exported the subnets to a spreadsheet and searched but no luck.

Does anyone know how can I fix it? Where can I find this object to delete/amend?
Thanks,