Problems with Updating to newest 3CX-Version

[walsermedia]

We can't upgrade to the newest 3CX version and always get the following error:

Hit:1 http://downloads-global.3cx.com/downloads/debian stretch-testing InRelease
Hit:2 http://security.debian.org stretch/updates InRelease
Ign:3 http://deb.debian.org/debian stretch InRelease
Hit:4 http://deb.debian.org/debian stretch-updates InRelease
Hit:5 http://downloads.3cx.com/downloads/debian stretch InRelease
Get:6 http://repo.saltstack.com/apt/debian/9/amd64/archive/2019.2.0 stretch InRelease [2,841 B]
Ign:7 http://deb.debian.org/debian jessie-backports InRelease
Hit:8 http://deb.debian.org/debian stretch Release
Err:9 http://deb.debian.org/debian jessie-backports Release
  404  Not Found
Hit:10 http://packages.cloud.google.com/apt cloud-sdk-jessie InRelease
Hit:11 http://packages.cloud.google.com/apt google-cloud-compute-jessie InRelease
Hit:12 http://packages.cloud.google.com/apt google-cloud-packages-archive-keyring-jessie InRelease
Hit:13 http://packages.cloud.google.com/apt google-compute-engine-jessie-stable InRelease
Reading package lists...
E: The repository 'http://deb.debian.org/debian jessie-backports Release' does no longer have a Release file.

 

[Saqqara]

i think Debian have removed the required packages

upgrade instructions https://www.3cx.com/docs/upgrading-pbx-v16/

 

[walsermedia]

we are already using 16.0.504

 

[cobaltit]

Do you mean 16.0.4.504? If so that is the latest release.

 

[walsermedia]

16.0.4.504 is the release which fails to install

 

[MichaelB_3CX]

Go to sources list and uncomment Jessie repo.