Hi. While this has happened to me before, I forgot to check on which devices my favored book would work. In this case, it's only Kindle Android, Tablets, Iphone etc. It cannot be downloaded to my Oasis.

I was wondering if there could be a solution to this. Could I theoretically extract whichever file this is in one device, and use Calibri to turn it into a working epub/mobi?

[CaptainKidd]

I'm not a Calibre user, but you can convert the book to AZW3 using this on-line converter. https://ebook.online-convert.com/convert-to-azw3
In the Optional Settings: Select Kindle Oasis from the pulldown menu, then change the title and author to your own preference of how you want it to appear on your device. (e.g. I prefer titles to be exactly as they appear on the cover and authors to be first name followed by last name vice last, first)
Copy the converted file into the documents folder of your Oasis.

I'm not a Calibre user, but you can convert the book to AZW3 using this on-line converter. https://ebook.online-convert.com/convert-to-azw3
In the Optional Settings: Select Kindle Oasis from the pulldown menu, then change the title and author to your own preference of how you want it to appear on your device. (e.g. I prefer titles to be exactly as they appear on the cover and authors to be first name followed by last name vice last, first)
Copy the converted file into the documents folder of your Oasis.

Thank you!