Is Debian 9.9.0 a version too far? My /etc/apt/sources.list in below
root@zoneminder:~# more /etc/apt/sources.list
#
# deb cdrom:[Debian GNU/Linux 9.9.0 _Stretch_ - Official i386 NETINST 20190427-1
1:18]/ stretch main
#deb cdrom:[Debian GNU/Linux 9.9.0 _Stretch_ - Official i386 NETINST 20190427-11
:18]/ stretch main
deb http://ftp.us.debian.org/debian/ stretch main
deb-src http://ftp.us.debian.org/debian/ stretch main
deb http://security.debian.org/debian-security stretch/updates main
deb-src http://security.debian.org/debian-security stretch/updates main
# stretch-updates, previously known as 'volatile'
deb http://ftp.us.debian.org/debian/ stretch-updates main
deb-src http://ftp.us.debian.org/debian/ stretch-updates main
# ZoneMinder repository
deb https://zmrepo.zoneminder.com/debian/release stretch/
root@zoneminder:~# apt update
Hit:1 http://security.debian.org/debian-security stretch/updates InRelease
Ign:2 http://ftp.us.debian.org/debian stretch InRelease
Hit:3 http://ftp.us.debian.org/debian stretch-updates InRelease
Hit:4 http://ftp.us.debian.org/debian stretch Release
Ign:5 https://zmrepo.zoneminder.com/debian/release stretch/ InRelease
Hit:6 https://zmrepo.zoneminder.com/debian/release stretch/ Release
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
root@zoneminder:~# apt install zoneminder
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package zoneminder
root@zoneminder:~#