Clicking a Google query link logs user out of session

I have a curious situation with my NodeJS server: it seems like searching for the website on Google signs out the user.

The homepage is https://emocoes.org/pt/inicio. I sign in to the website and the homepage shows the version for users, such as a "Content list" button.

I open a new tab, search for the website on Google and click the link. Now the homepage no longer shows the version for users. It's as if I had signed out. When I refresh the first tab with the member version of the homepage, it also shows the public version. I checked that the cookie for session in the session store still exists.

The URL from the Google query is:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjC2J3D65H4AhX5Q_EDHRpnCvoQFnoECAYQAQ&url=https%3A%2F%2Femocoes.org%2Fpt%2Finicio&usg=AOvVaw15-Ef1H79pA6DxaHMLJfgC

I do not see any issue in this link.

I added this tracing to the server's route for the homepage:

router.get("/pt/inicio", async (req, res) => {
  console.log("URL = %o", req.originalUrl);
  console.log("query = %o", req.query);
  console.log("User = %o", req.user);
  // The result after the Google URL is:
  //[2022-06-03T17:40:21.308Z] URL = '/pt/inicio'
  //[2022-06-03T17:40:21.308Z] query = {}
  //[2022-06-03T17:40:21.309Z] User = undefined
  ...
});

Since the session exists in the MongoDB store, it's as if clicking the Google link deletes the cookie in the browser. I have Safari on macOS but the same thing happens to another user on Windows and Google Chrome.

How can I debug this issue?