I couldn’t install Anki on Arch Linux through the AUR.
My keyserver was set to
keys.openpgp.org. You didn’t upload the keys there.
What fixed it was:
gpg2 --keyserver hkps://keyserver.ubuntu.com:443 --recv-keys 3F5566A2D16899FB
However, it would be great if you could add your keys to the following key servers: