k2u3’s request is seconded. Could someone explain exactly how to check the installed version of Widevine, and how to update it if it’s not the most recent one?
First you need to go into the Information page of the Netflix addon by using the context menu. Once there, go to Dependencies on the bottom, then down to InputStream.Helper.
Click on that, and press Configure. There you should see the Troubleshooting page.
If this does appear, go to InputStream Helper information where it should tell you what version of Widevine you have installed. If it’s not the most recent, on the Troubleshooting page you can go down to (Re)install Widevine CDM library, and update there.
If the Troubleshooting page doesn’t appear, you may have to update InputStream Helper. On the InputStream Helper addon page, instead of clicking on Configure, click on Update.