Cloudmin Xen GPL Debian repository - Binary is not signed


When installing Cloudmin Xen GPL version i got this error on apt update:

apt update

Get:1 stretch/updates InRelease [94.3 kB]
Ign:2 stretch InRelease
Ign:3 binary/ InRelease
Get:4 stretch-updates InRelease [91.0 kB]
Get:5 binary/ Release [1,382 B]
Get:6 binary/ Release.gpg [173 B]
Hit:7 stretch Release
Ign:6 binary/ Release.gpg
Reading package lists… Done
W: GPG error: binary/ Release: The following signatures were invalid: 1719003ACE3E5A41E2DE70DFD97A3AE911F63C51
E: The repository ‘ binary/ Release’ is not signed.
N: Updating from such a repository can’t be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

the installer script did install the GPG key successfully.

i also tested APT repo of KVM: and the GPG key works, i could do apt update on KVM repository successfully.

so i’m suspecting there is something wrong with repository