If you have a free ShapeDiver account, only the trial version of Karamba works. This version is limited to 20 beams & 50 shells, if your model produces more than that the computation will fail. We will work on a more explicit error in this case.
If you need to use a commercial version of Karamba, please contact us to discuss your options.
As you mentioned in your post, it is likely that the problem happens because you are using Rhino 7 locally and uploading to a system that runs Rhino 6. Did you try to open your definition in Rhino 6 to check what happens?
Additionally, even if you manage to upload the file, you will likely still run into trouble with Karamba because a PRO account does not come with the professional version of Karamba (see my answer above).