Okta sign up responses with E0000060 error code

Question

I'm configuring authentication with Okta service. I'm using angular framework and okta signin widget. I also added feature flag to my OktaSignIn object and configured Okta service with admin console:

this.oktaSignIn = new OktaSignIn({
  logo: 'assets/images/logo.png',
  baseUrl: myAppConfig.oidc.issuer.split('/oauth2')[0],
  clientId: myAppConfig.oidc.clientId,
  redirectUri: myAppConfig.oidc.redirectUri,
  authParams: {
    pkce: true,
    issuer: myAppConfig.oidc.issuer,
    scopes: myAppConfig.oidc.scopes,
  },
  authClient: oktaAuth,
  features: {
    registration: true
  });

But after clicking "sign up" button on widget HTTP GET request to https://dev-XXX.okta.com/api/v1/registration/form responses with E0000060 error code.

{
  "errorCode": "E0000060",
  "errorSummary": "Unsupported operation.",
  "errorLink": "E0000060",
  "errorId": "oaeFIcE87d5SxSNJ9Z19tIomQ",
  "errorCauses": [ ]
}

Am I setting up the Okta service incorrectly?