Go to
Settings > apps > dual apps
Click the gear icon at the top right and select "delete dual apps account"
Reboot
Or if using dual apps
Settings > apps > dual apps
Search for and enable "WebView"
Then try to enable the WebView again from developer settings
If there's a new version, you don't have to "put" it.
Android system WebView is updated from playstore.
anyway, i was able to download and install the updated apk the normal way.