I've been using v2.5.6 continuously with Waterfox Classic (FF56 based), but it can't catch logins anymore

Little to add to the title. I’ve been using this version for a long time since this was the last one labeled to support FF56. And it was working fine, but a while ago (a few months perhaps) it stopped being able to catch logins. So I can’t save any new ones. What on earth might have happened?