Can you show me how your requirement looks in the project explorer, if it got a documentKey attribute?
If it does not have a documentKey attribute, can you confirm you can add this attribute by right-clicking on the requirement?
From what I see, there is a problem with how your object attributes in your ReqIF files are mapped to the created requirements. I do not know well this part of the add-on, ie how to configure the mapping, there is something on this in the embedded documentation and you may also have a quick look at this thread: [Requirement] Importer Preferences
Stephane