A far as it looks for me the problem is not HP's site change. With every HPLIP release I (as the maintainer of the OpenPrinting web site) get the plugin e-mailed from a person of the HPLIP team and upload it to the appropriate place on the OpenPrinting web server. I checked and I actually got plugins for 3.17.6 and 3.17.10 (which I both have uploaded) but not for 3.17.7 and 3.17.9.
So the problem is that HP did not supply the plugin for 3.17.7 and 3.17.9.
A far as it looks for me the problem is not HP's site change. With every HPLIP release I (as the maintainer of the OpenPrinting web site) get the plugin e-mailed from a person of the HPLIP team and upload it to the appropriate place on the OpenPrinting web server. I checked and I actually got plugins for 3.17.6 and 3.17.10 (which I both have uploaded) but not for 3.17.7 and 3.17.9.
So the problem is that HP did not supply the plugin for 3.17.7 and 3.17.9.