What version of Inkscape were you using? Have you looked to see if you still have that version downloaded and stored somewhere on your computer (check your downloads folder for instance.) you could also look for that older version on line, but be careful as you don’t want it “bundled” with other software that could be malicious. As a final option, if you don’t have it stored elsewhere, or cannot find it anywhere else, you could try to do a “restore” on your computer back to a date from before you deleted and installed a newer version. If you don’t know how to do this, research it first before trying or find someone to help you who is familiar with doing it.
If you find that you do have the old version still somewhere, be sure you back it up and store it away for future needs like this. You might also look to see if you are missing a driver but I am not sure where you check for that. Does Signcut not have a website that you could reach out to since your dealer is no longer in business?
I did a quick search here on the forum for old threads on “Signcut” and found some really old ones from back in 2013 and old versions of the software, one I saw suggests that you need to uninstall both programs (keeping Signcut serial number and registration number) and then reinstall. Not sure if that will work for you or not. I suggest you search for those old threads and review and see if you find any info. that might help you sort out your issue.
I believe this is where you go to find Signcut suppprt:
https://signcut.freshdesk.com/support/homeI am afraid that is really the only advise I have. I never used Signcut with my cutters and I don’t think Sherri sells it or provides support for it via the US Store. I believe only Dawn did in the UK. If all else fails, you could look at getting SCAL to run your machine perhaps. Not ideal, but not too expensive and wouldn’t leave you dead in the water.