authClient.session.exists() return false after login due to 3rd party cookies blocked default

If Block third-party cookies for all browsers

After login authClient.session.exists() return false and redirect to logout.

/api/v1/sessions/me is not found 404

How to allow third-party cookies in okta?

authClient = new OktaAuth({
issuer: oktaIssuerUrl,
clientId: oktaClientId,
redirectUri: oktaRedirectUri,
postLogoutRedirectUri: oktaLogoutUri,
scopes: [‘mira-session’, ‘openid’, ‘offline_access’],
tokenManager: {
autoRenew: true,
expireEarlySeconds: 120,

As you mentioned, the problem isn’t with Okta, but your browser settings. With 3rd party cookies blocked, the only way to make this call work is if your application is on the same domain as your Okta domain.

More information here: FAQ How Blocked Third Party Cookies Can Potentially Impact Your Okta Environment | Okta Help Center

Without enabling the third-party cookies, it will not work. If the end-user does not enable the third-party cookies then how will manage the session?

As mentioned in that article I shared, if you set up a custom domain and host your application on the same domain, the cookies will no longer be considered third part and your application will be able to access the Okta session cookie.