Please ensure you are using the template that came along with the installation. A .csv template can be found inside the installation directory. Also, let us know if you are using the latest OneCollect 1.6 version.
If that does not solve, you may copy the template you use here (after removing/masking credentials). We can check issue with file and send you updated one.
I will send a sample with 100 dummy ESXi hosts, pm your email address. Also note that for ideal performance, it is recommended to limit to 50 hosts per job. But that is not a hard limit and that should not block the import.