import html file from raindrop not working

trying to import html files generated by raindrop.io but it's showing 0 not yet imported.
I tried both the raindrop backup html containing all bookmarks, and separate exports by collections (export 1 html per tag - or space in memex jargon).
tested with latest chrome/vivaldi on windows.

devtools show multiple erros POST http://localhost:11922/status net::ERR_CONNECTION_REFUSED

is it parsing the files in the background for a very long time without visual hint / progress bar ? or is it just not working ?

I had imported bookmarks previously from a diigo export. Will it detect duplicates and merge them ? or will it stop on suplicate errors ? or will it just add duplicates ?