U2F (fido) authentication not supported

At work, we use 'okta' to do Single Sign On (SSO) using various web-apps, including gmail. When adding a google account, a window pops up asking for google credentials, which in turns redirects to the okta login. On the okta login we have set up yubikeys enabling U2F. However the used browser does not seem to be supported (there is no browser check per-say, firefox threw the same message until enabling u2f in about:config.