DNF can't upgrade/install any packages
I just finished installing a dual-boot Windows 10/Fedora 25, and successfully logged in to my Fedora account. However, upon trying to install any packages, I keep getting the same error that "Downloading successful, but checksum doesn't match. I've tried sudo dnf clean all, and it doesn't help. When I try to do dnf upgrade, I get even more errors: "not found updateinfo for: Fedora 25 - x86_64" -> "Downloading successful, but checksum doesn't match." for all downloads -> "Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried." -> "Failed to synchronize cache for repo 'updates'." I have absolutely no idea how to fix this. Please help!
For what it's worth, I've noticed that my DNF version is 1.1.10, but I also have no idea how to upgrade to the latest, considering "dnf upgrade" is broken.