Supabase signUp returning AuthRetryableFetchError 504

I have an application built in Next.js with Supabase.

It uses Supabase methods for sign up and login. Login works normally, but sign up stopped working (it worked as expected 3 days ago, but now not anymore).

...

console.log(validation); 
/* {
  success: true,
  data: {
    password: 'test',
    repeat: 'test',
    email: 'test@test.com'
  }
} */

if (validation.success) {
     const { email, password } = validation.data;
     const { error } = await supabase.auth.signUp({ email, password }); 

     if (error) {
        console.log(error);
        console.log(JSON.stringify(error)); // {"__isAuthError":true,"name":"AuthRetryableFetchError","status":504}
        return {
          message:
            error.status == 504 ? `Please try again later.` : error.message,
        };
     }
...
}

I checked in my Supabase database and I am getting that project status is okay and everything with auth.

User can be added to Authentication table normally (using Supabase dashboard, manually), but through code, in my app, I always get error {"__isAuthError":true,"name":"AuthRetryableFetchError","status":504}. Console is empty or doesn't give any useful information.

What can I try next or how to fix this?

The problem was in my SMTP provider - Resend. Their servers were down. You can check it here.

The solution was to disable email confirmation in Supabase Authentication -> Providers -> Confirm email (as long the Resend servers were down).