Welcome to the forum!
Sorry to hear about your problems. I'm afraid I can't decipher the Traceback reports, hardly at all. The last line seems to indicate the extension can't find that path. Or can't find that file at that path. If you really have entered a path somewhere which starts with "u'C:\\" I might guess that the "u' " is the problem. Although the double backslashes seem odd. The only thing else I can really say about the error, is that there might be more than one problem. But other members might know a little more.
Since I haven't seen any messages about SignCut in a while, I tried looking up where it can be downloaded from, to refresh my memory. I can't seem to find it. I've found where it used to be, or maybe is supposed to be. Maybe that site is having problems today, or something. But the link shown on
this page gives Not Found error. Where did you download it from?
My first thought, assuming it's still being developed, or at least supported (I mean the Inkscape extension) is that you should contact the SignCut people about it. It's possible they are no longer supporting it, which would mean it probably can't be fixed. And that would mean you'll have to find some other Inkscape tool, feature or extension, to do your cutting.
Hhm, well I found a
statement that Windows 10 is supported by SC, which perhaps is an indication that they would fix it. Ok, so I think your first step should be contacting them. When you do, also double-check and make sure that you have the most current version, and the correct version. There's probably some info about how to get support, somewhere in the files you downloaded and installed.
Would you let us know what you learn from them? It will help us know how to help other SC users in the future.