DRM error from Project Gutenberg on (Kindle) Fire 10

For several years I had downloaded books from Project Gutenberg to my (Kindle) Fire 8. This was particularly useful when I wanted to read something in an environment where direct internet connection was impossible or a hassle. I recently upgraded to a Fire 10 and I am suddenly getting a “DRM” error on the downloaded file, even when I have specifically used the Kindle icon in Project Gutenberg and even though the file has been sent using a “.mobi” extension.
I get the same error on attempts to download using EPUB (extension “.epub”). Kindle will open a download using Plain Text UTF-8 (extension “.txt”), but the text can be difficult to follow and tools such as bookmark are not available. (Reading The Brothers Karamazov in one pass has been a bit difficult without the ability to note where I left off.)
I even tried downloading books that I know had been on my earlier Fire 8 tablet but I get the same error.

I have not (yet) found any instructions on my new Fire unit to avoid this problem. The tablet is “vanilla” and I have made no changes to the set-up process.

Suggestions (instructions) would be most helpful. Thanks.
Tom~

I’ve downloaded tons of books from gutenberg.org for my Kindle, and I always had the option to choose the native Kindle file format. Never had a problem. I have a Kindle Paperwhite though, but I can’t imagine that it makes a difference on a Fire. So try downloading those books in Kindle format.

ETA: just reread the OP, and I saw that you downloaded .mobi files. That’s as far as I remember also the format you get when you go to the “Download for Kindle” button on Gutenberg. Sorry, in this case I have no solution.

As an experiment, I just now tried downloading and opening a book from Project Gutenberg on my Fire 10 (which may not be the latest version), and I experienced no problems. So, I don’t know why you’re having problems.

What do you mean by “the Kindle icon in Project Gutenberg”? I’m not seeing icons, just hyperlinks.

Sorry. It was not an icon. As you say, just a link.
I have been wondering whether I toggled a wrong switch as I set up my new Kindle, but I cannot figure out what it might have been.

To the OP, I suggest this forum: https://www.mobileread.com/

I use a Kobo, so I doubt I can give you any useful advice.

It’s not surprising that you can’t open EPUB files; as far as I know the Kindle app doesn’t support this format. But I am stumped as to why you can’t open files that are in a proper Kindle format. I didn’t think files from Project Gutenberg had DRM.

For what it’s worth, in my experiment just now, I used the Fire’s Silk browser to go to Project Gutenberg’s webpage and downloaded a book from there (and didn’t have any trouble opening it). But it should also be possible to download Project Gutenberg files on a computer and then transfer them to your Fire either by email or USB cable.

If you still can’t figure out why things aren’t working for you, you could try, as a last resort, either downloading and using a different e-reader app on your Fire tablet, or obtaining your books from a different source than Project Gutenberg (manybooks.net is one other site that offers free public domain ebooks; and on Amazon’s own site some, but not all, public domain books can be found for free).

Thank you.
As it turned out, I had transposed two letters in one of my parms when setting up a new Fire. I finally found it after doing the ancient programming method of reviewing every single line in all my set-ups.

Update: If I understand correctly, Amazon has recently added EPUB support to its Kindle devices and apps.