Err http://ftp.debian.org jessie-backports/main amd64 Packages
404 Not Found [IP: 22.214.171.124 80]
Fetched 14.2 kB in 2s (5,145 B/s)
W: Failed to fetch http://ftp.debian.org/debian/dists/jessie-backports/main/binary-amd64/Packages 404 Not Found [IP: 126.96.36.199 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
I think they have removed the backports and it’s time to upgrade to Debian 9 or 10..