404 is a valid response code when using the client library to look for a user by email.

If the user exists you’ll get 200 and if the user does not exist you’ll get 404.

If you are using the client in the browser and don’t want to expose the 404 to the console, adding a try/catch would be a good idea. The 404 is the expected response code when the user does not exist:
https://fusionauth.io/docs/v1/tech/apis/users#response-2