looks like the last 4.9 kernel upgrade missed meta package linux-image-amd64
root@localhost:~# apt search linux-image-amd64
Sorting... Done
Full Text Search… Done
linux-image-amd64/jessie-backports 4.9+78~bpo8+1 amd64 [upgradable from: 3.16+63]
Linux for 64-bit PCs (meta-package)
linux-image-amd64-dbg/jessie-backports 4.9+78~bpo8+1 amd64
Debugging symbols for Linux amd64 configuration (meta-package)
root@localhost:~# apt-get install linux-image-amd64
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
linux-image-amd64 : Depends: linux-image-4.9.0-0.bpo.1-amd64 but it is not installable
E: Unable to correct problems, you have held broken packages.
root@localhost:~# apt search linux-image-4.9.0-0.bpo.1-amd64
Sorting... Done
Full Text Search… Done
root@localhost:~# apt search linux-image-4.9.0-0.bpo.2-amd64
Sorting... Done
Full Text Search... Done
linux-image-4.9.0-0.bpo.2-amd64/jessie-backports 4.9.13-1~bpo8+1 amd64
Linux 4.9 for 64-bit PCs (signed)