There has been an update (4 days ago) to inputstream.helper, the addon that downloads the widevine libary.
So I recommend this:
rm -r /home/osmc/.kodi/cdm
cd /home/osmc/addons
wget https://github.com/emilsvennesson/script.module.inputstreamhelper/archive/master.zip
mv master.zip script.module.inputstreamhelper.zip
In kodi:
goto Settings->Addon browser->install from zip
Navigate to Homefloder->addons
choose script.module.inputstreamhelper.zip
Run netflix again, if that doesn’t work run my Netflix-prep script and it downloads the latest Netflix addon again.