Assegnate 4 su 5 stelle

Tried to add this to Palemoon 24.7.1(86) in Win8.1 32bit and received this error: Pale Moon could not install the search plugin from "https://addons.mozilla.org/firefox/downloads/latest/89654/addon-89654-latest.xml?src=collection&collection_id=87651921-2f85-e26c-0061-06efecc8e56f" because an engine with the same name already exists.
Since no clue as to the identity of the conflicting addon is provided, I removed all addons having anything to do with searching in function or name, to no avail. Googling this error type produces many instances of search engine option addition problems and and eclectic set of other issues but no non-major effort "might work" solutions.
This addon installed fine in a practically virgin install of the latest FireFox though.