Error trying to export requirements to HP ALM with Excel Add-In

I am getting the following error when I choose the Entity Type (Requirements) from the Field Mapping form.

 Error happeded when communicating to ALM server:

Value cannot be null.

Parameter name: value

I am logged into my ALM project in both Excel and  ALM itself.

This is my first time trying to upload.

Any ideas?

Thanks in Advance,

Sufa