Stopped working when FF E10S dropped; nothing since. Abandonware. Rated 1 out of 5 stars
Used to be simply the best screenshot extension -- clean, reliable, etc. So much so, staff here bought a dozen+ copies, back when it was still "buy" rather than "free, but contribute". And recommended it to everyone who asked ...
Since then, and the arrival of E10S in FF, it's non-functional. Repeated communications with the developer just get "looking into it" or "working on it" . A few MONTHS later, still nothing.
Repeated empty promises over time == abandonware.
not abandoned, but e10s support is not ready
We hear your frustration. Migrating Page Saver to the e10s architecture turned out to be more time-consuming than we anticipated, and unfortunately other work has gotten in the way of us completing that project. And in truth it may make sense to migrate to the new WebExtension API at the same time (but doing so will require us to remove some important Page Saver features such as command line support, so that is not an easy decision for us).
I will add that for most people lack of e10s support is not currently a big problem because e10s is not enabled by default in Firefox when incompatible add-ons are present. But enabling e10s enhances security and stability in important ways, so I understand why you want to turn it on.