I’m also seeing this same issue with some client sites. The first ‘/’ in the wc-auth url’s is being urlencoded and resulting in a 404 when trying to authenticate. If I manually replace the ‘%2F’ with the decoded ‘/’ the page will load correctly, but then the next page in the auth flow does the same thing. There definitely seems to be an issue with the redirects within the auth flow on the woocommerce or wordpress side.