QR codes used to work, images now gone

I created several QR codes a couple months back, but today discovered that the PNGs no longer exist, as in, the entry in the backend of wordpress shows a broken image icon in some of the entries listed on the QR Redirects admin page. I had saved a list of these links to the PNGs when I created the QR codes, so now when clicking on the link to retrieve the image for use on prints now gives me a “not found” wp page on my site. From a support ticket i read on the QR Redirector forum, I have already tried opening permalinks settings and without changing just saving but no change. I have dozens of older qr codes that work fine still. How can I regenerate the PNgs WITHOUT changing the actual QR info in them? Some of them were already printed, but I still need access to them to download and send to be printed on other items, and I don’t have access to the originals because they always just worked. The page I need help with: [ log in to see the link]