“Gradle Wrapper is not available” most probably means that the project you are trying to import does not have the four Gradle Wrapper files that practically any Gradle build should contain in their source code, as it defines exactly which version of Gradle to use to execute the build and thus prevents failing builds because of version conflicts / breaking changes done in Gradle: The Gradle Wrapper.
Regarding the “Could not find …”, these are strange.
I just tried to download the file from the given URL and it works perfectly fine.
So I’d say just retry it, maybe with --refresh-dependencies from the command-line in case Gradle remembers it didn’t find them.
If it still does not work, I’d suspect some firewall, proxy, or anti-virus that is intervening on your side.