This usually happens when Manjaro doesn’t carry a package that Arch does carry (and that the package you’re trying to install from the AUR depends on).
This is always a risk when combining Manjaro with the AUR, as Manjaro is a few weeks behind Arch when it comes to packaging. You can try if the beta repositories have the package, but otherwise you’ll just have to wait for Manjaro to update its packages. It’ll probably resolve itself, eventually.
You can try looking on the Manjaro forums (I don’t see a workaround other than switching to testing/unstable) to check if there’s a fix, but please don’t bother the Arch/AUR people, they can’t help you.