Which OFED did you install? Is it MLNX_OFED driver? If so, you should install the driver with the -with-vma flag.
Yes, it was MLNX_OFED driver. I didn't use install script, but did mostly the same thing that -with-vma flag does.
I would suggest to validate offloading using 'sockperf' first and in addition to open an issue on VMA home page (https://github.com/Mellanox/libvma )
VMA is opensource, but its support is not free. If your company has VMA support contract, you'll be all set.