Can't perform update when double nat'ing

[Richard Shaw]

I know the default answer, don't double nat, but in this case what I'm
doing is that I have a wireless travel router with WISP and I am using it
to create my own private & secured network behind a public network.

Web browsing works fine but when I try to perform a "dnf update" I get a
"Error: Failed to synchronize cache for repo 'updates'."

Since it's simple download, i,e, not a complicated connection like a VPN. I
don't know why it wouldn't work, but it apparently does not.

Ideas?

Thanks,
Richard