Hi, all you have to do is replace the "widevinecdm.dll" file located in the "Kodi>cdm" subfolder.
I don't know how to find it in Google, but since I had an old installation of the add-on, I got it from there.
I've uploaded version 4.10.2891 at this link in case you'd like to download it: https://we.tl/t-nBplvF4Na7
I can't downnload the file, literally I don't see it...